An assembly method for an endoscope image pickup unit including a distal end portion main body portion including a front opening portion, a side opening portion, a rear opening portion and an arrangement space portion, a lens section including a distal end lens having an outer diameter that generally fits in the front opening portion, and an image pickup section that fits in the rear opening portion and includes an image pickup device arranged in an image forming position by a lens system such as the lens section, the assembly method including an inserting step for inserting the lens section into the arrangement space portion from the side opening portion, a fitting step for fitting the inserted lens section in the front opening portion, and an image pickup section fitting step for fitting the image pickup section in the rear opening portion from a rear of the rear opening portion.
