A projection display device includes a screen for having projected images displayed thereon, a main frame overlaying the top edge and the bottom edge of the screen, a pair of side frames adjustably secured to opposite two sides of the main frame to change transverse distances between the side frames, each of the side frames holding one of the side edges of the screen, and a pair of securing members selectively securing the side frames to the main frame at different positions so as to adjust a viewable size of the screen to present different aspect ratios. An electronic apparatus utilizing the projection display device is also disclosed.