onrenderimage not called on android platform.

Hello. I want to make some postprocessing effect. so I made it using onrenderingimage function.

It work well in unity editor, but It doesn't work in mobile platform. I found onrenderimage function is not called in mobile platform(Nexus7 & Galaxy2).

Can I use onrenderimage function in mobile platform? Do you know any idea in this problem ?

Thank you for reading this question.. :)