On CentOS release 6.7, there's file system problem.
Aftert reboot /home is set under /home (/home/home) like followings.

# ls -l /home
total 48
-rw------- 1 root root 7168 Nov 15 19:10 aquota.group
-rw------- 1 root root 7168 Jan 25 11:09 aquota.user
drwxr-x--- 2 root root 4096 Jan 18 21:55 backups
drwxr-xr-x 4 root root 4096 Jan 1 11:59 home
drwxr-xr-x 8 root root 4096 Apr 5 01:10 log
drwx------ 2 root root 16384 Nov 15 18:58 lost+found
drwxr-xr-x 6 mysql mysql 4096 Dec 13 22:34 mysql


# df
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/mapper/VolGroup-lv_root
12778200 2946824 9175608 25% /
tmpfs 961176 0 961176 0% /dev/shm
/dev/vda1 487652 205564 256488 45% /boot
/dev/vdb 41153856 549492 38507212 2% /mnt/extradiskA
/dev/vdb 41153856 549492 38507212 2% /home

I have set on fstab /home with 'mount bind' but it seems like bind is not effective.

/etc/fstab is following.

# cat /etc/fstab

#
# /etc/fstab
# Created by anaconda on Mon Jul 28 08:21:01 2014
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
/dev/mapper/VolGroup-lv_root / ext4 defaults,usrquota,grpquota 1 1
UUID=9a855356-ee00-4ae7-a185-226566ce1dba /boot ext4 defaults 1 2
UUID=093c9b95-8336-4682-9927-132dbdf2f082 /mnt/extradiskA ext4 defaults,usrquota,grpquota 1 2
/dev/mapper/VolGroup-lv_swap swap swap defaults 0 0
tmpfs /dev/shm tmpfs defaults 0 0
devpts /dev/pts devpts gid=5,mode=620 0 0
sysfs /sys sysfs defaults 0 0
proc /proc proc defaults 0 0
/mnt/extradiskA/home /home none bind 0 0
/mnt/extradiskA/log /var/log none bind 0 0
/mnt/extradiskA/mysql /var/lib/mysql none bind 0 0
/mnt/extradiskA/.backup /.backup none bind 0 0
/mnt/extradiskA/.daily_backup /.daily_backup none bind 0 0
/mnt/extradiskA/backups /var/backups none bind 0 0

It appears to be doing what you asked. The /home shows the same details in df as /mnt/extradiskA because the bind mount is simply remounting the SAME device in a different location accordingly you'll see the SAME device and usage in df.

/dev/vdb 41153856 549492 38507212 2% /mnt/extradiskA
/dev/vdb 41153856 549492 38507212 2% /home

If you do ls -l /mnt/extradiskA do you see a subdirectory called home there?

If you do ls -l /mnt/extradiskA/home and ls -l /home do you see the same files in both? If so the bind mount worked.

The bind mount while it does make the mount restricted to the subdirectory you specified (/mnt/extradiskA/home in your case) it does NOT limit the size to that subdirectory - the size is based on the underlying mount just as if you ran "df -hP /mnt/extradiskA/home" would show you the underlying mount, /mnt/extradiskA.

The problem is not mounted.
'/mnt/extradiskA/home /home none bind 0 0' on fstab is not recognized correctly.
It is interpreted not bind type.
So df shows '/dev/vdb 41153856 549492 38507212 2% /home'
Do you know how to fix?

It IS mounted if df shows that.

You appear to be thinking it will show the device as /mnt/extradiskA/home but as I noted in my previous answer it actually will show the real device which is /dev/vdb.

I suspect what you're seeing about the bind type is occurring because you're trying mount /home again even though it is already mounted.

What happens if you:
a) umount /home
b) df /home
c) mount /home (with no other options on command line)
d) df /home (again)

Be sure to provide full output rather than summarizing so we can see the exact errors if any.