Get fuse-exfat
$ sudo add-apt-reprository ppa:relan/exfat
$ sudo apt-get update
$ sudo apt-get install fuse-exfat

Create mount point.
$ sudo mkdir /media/Data

Manually mount:
$ sudo mount -t exfat-fuse /dev/sda6 /media/Data
umount:
$ sudo umount /media/Data

Automatically mount (by edit fstab):
$ sudo gedit /etc/fstab
add new line
/dev/sda6 /media/Data exfat-fuse defaults 0 0
save and restart.

*1 '/dev/sda6' is Device ID, could be '/dev/sdXX', such as '/dev/sdb1', please check in Disk Utility.
*2 Someone says, update util-linux-ng 2.17 to 2.18, ubuntu will identify exfat automatically, but still need fuse-exfat. (actually not test)