An endoscope includes: an observation through hole which is formed in a distal end portion body, an opening shape of the observation through hole being defined by a pair of long sides which face each other and a pair of short sides which face each other； grooves for cutting machining clearance, the grooves being formed at four corners where the long sides and the short sides respectively intersect with each other during machining the observation through hole； an observation lens being inserted into the observation through hole； and an adhesive material which is circumferentially disposed between the observation through hole and the observation lens. In such an endoscope, each groove is formed in contact with the short sides, and projects toward the outside of the observation through hole from the long sides.
