Like the subject asks, who invented Pac-man? Might as well ask, who invented Pong? What that the first video game?

I think this site can answer all that for ya ;)

http://www.designboom.com/eng/education/pong.html

The name of Pac-Man's creator was Toru Iwatani. The creator of Pong was Nolan Bushnell.

This Page (http://www.osti.gov/accomplishments/videogame.html) tells about development of a tennis video game in 1958.

I gotta say that I was shocked to find out that Pac-Man was developed in the late 70's, I always thought it was the 80's, but tonight on the "American Bandstand 50th Anniversary" they had it in the 70's segment! Wow, learn somethin' new everyday! :)