In each odd-numbered frame, a game image generated by a three-dimensional image processing unit 31 is supplied to a first LCD 11, and then a game image identical to the generated game image is stored in a first VRAM 21a. Also, a two-dimensional image processing unit 37 supplies the game image stored in the immediately-preceding even-numbered frame in a second VRAM 21b to a second LCD 12. On the other hand, in each even-numbered frame, a game image generated by the three-dimensional image processing unit 31 is supplied to the first LCD 12, and then a game image identical to the generated game image is stored in the second VRAM 21b. Also, the two-dimensional image processing unit 37 supplies the game image stored in the immediately-preceding odd-numbered frame in the first VRAM 21a to the first LCD 11. With this, in a portable game machine including two display units, different three-dimensional game images can be simultaneously displayed by a single three-dimensional image processing unit on the two display units without flicker on the display screens.