An image pickup apparatus has a construction in which a diffraction
element is provided in an observation optical system. Zero-order light
that is transmitted straight through the diffraction element and one of
the +1st-order diffracted light and the -1st-order diffracted light that
is diffracted by the diffraction element are imaged onto an image pickup
surface of an image pickup apparatus. The imaging areas of the zero-order
light and one of the +1st-order diffracted light and the -1st-order
diffracted light that is diffracted by the diffraction element do not
overlap on the image pickup surface of the image pickup apparatus. With
this construction, a small image pickup apparatus that provides a
high-resolution spectral image and a color image of an object can be
obtained.