The invention provides an endoscope and a method of assembling the endoscope. According to an aspect of the invention, the circumferential position of a protrusion portion (96A) of a light guide member (78) is aligned with the position of a second groove portion (112A) of a pressing member (58) and a tip portion (78A) of the light guide member (78) is inserted into an insertion hole (112A). Next,the light guide member (78) is rotated to align the circumferential position of the protrusion portion (96A) of the light guide member (78) with the position of a first groove portion (70A) of a mounting hole (70A), and the tip portion (78A) of the light guide member (78) is mounted in the mounting hole (70) of a tip portion body (48). After that, a screw member is inserted into a through hole (104) of the pressing member, is threadedly inserted into a screw hole (102) of the tip portion body (48), and fixes the pressing member (58) to a base end face (56) of the tip portion body (48).