In a folding mobile phone (folding portable electronic device), a cam mechanism (support mechanism) includes a first guide groove, a second guide groove, a first guide pin engaged into the first guide groove, a second guide pin engaged into the second guide groove, and a link member connecting the first and second guide pins. The cam mechanism supports a liquid crystal display part to allow the liquid crystal display part to turn clockwise and counterclockwise as viewed from the front, thereby allowing the liquid crystal display part to be changed between a vertical position and a horizontal position. Furthermore, the cam mechanism includes an urging mechanism urging the second guide pin to allow the liquid crystal display part to reach the vertical or horizontal position in either turning direction.