The 34-year-old has played gay characters on screen in films like "Milk" and "Blind Spot" and he also famously shared a same-sex kiss with Will Forte on US sketch show Saturday Night Live in 2009.
Many have questioned the actor's sexual orientation but Franco insists he is not offended by all the speculation, reported Huffington Post.
"In high school these girls got mad at me and so they spread this rumour that I was having a gay relationship with one of my closest friends. And they even made up a little dance they would do in the girl's locker room about me being gay. I still don't know what the dance was.
"It wasn't like it was anything new. And, in fact, it wasn't something that frightened me... If people think that, it's fine. I really don't care."