An endoscope includes in order from an object side, an objective optical system, an optical-path splitter, an image sensor, and an image processor. A λ/4 wavelength plate is disposed between the objective optical system and the optical-path splitter. The optical-path splitter includes in order from the object side, a first prism and a second prism, and has a beam splitting surface at which the first prism and the second prism are brought into close contact. The optical-path splitter splits light at the beam splitting surface, into a first optical path through which P-polarized light is transmitted and a second optical path through which S-polarized light is reflected. The first prism and the second prism, by sliding the beam splitting surface, adjust an optical path length of the first optical path and an optical path length of the second optical path, and are disposed at positions of cancelling an amount of shift in a focusing position of extraordinary light and a focusing position of ordinary light, and satisfy specific conditional expressions.
