Endoscope

An endoscope comprising an insertion portion that includes a distal end portion, and a bending portion configured to change a direction of the distal end portion, the bending portion being provided so as to extend from the distal end portion, wherein:

• the distal end portion includes a casing having a round shape in a cross-section, and an image pickup module that includes an optical module section including a plurality of optical members and an image pickup sensor, the image pickup module having a rectangular shape in a cross-section;
• the image pickup module includes a semiconductor stack in which a plurality of semiconductor devices is stacked;
• an entirety of the image pickup module is completely housed inside the casing;
• an end of an operation wire configured to bend the bending portion is fixed in a space over a side face of the image pickup module;
• and
• a maximum length of a cross-section of the space is no less than 100% and no more than 112.5% of an outer dimension of the fixed end;
• the operation wire having a round shape in a cross-section;
• and
• a diameter R50 of the operation wire, a length D30 of the image pickup module and a diameter R40 of the casing meet the following expression:
• (R50+D30+R50)≤R40≤1.25×(R50+D30+R50).