A projection optical system that performs enlargement projection of an image on a display device surface formed of a plurality of pixels onto a screen surface, in which pixel shift by less than a pixel pitch is performed on the screen surface in a vertical direction, a horizontal direction, an oblique direction, or a vertical and horizontal directions, and in which conditional formulae (1) and (2) below are fulfilled over the entire image range: (1)|ΔΔRG|≦0.5 d and (2)|ΔBG|≦0.5 d, where d represents the amount of pixel shift (>0), ΔRG represents lateral chromatic aberration in the direction of pixel shift of colored light R having a wavelength of 640 nm with respect to colored light G having a wavelength of 546 nm, and ΔBG represents lateral chromatic aberration in the direction of pixel shift of colored light B having a wavelength of 450 nm with respect to the colored light G having a wavelength of 546 nm.