Download GAppsInstaller for Lollipop.
http://dn.odroid.com/GAPPS/GAppsInstaller_lollipop.apk
Install GAppsInstaller.
But failed.
Get root permission.
Click Build number many times.
Now find Developer options.
Root access.
go back Setting and enter Privacy.
Privacy Guard.
Check 'Enabled by default and Gapps Installer item'
Now Can install.
Reboot and go 'Play Store'.