Provided is an endoscope that includes an airtight casing which accommodates an imaging device and first signal lines in an airtight state therein and that can connect proximal ends of the first signal lines and a signal relay part together without securing an extra length for the first signal lines. An airtight casing 10 is disposed inside an outer tube 132 of an insertion part 102, an imaging device 114 and first signal lines 116 are accommodated inside the airtight casing 10, a distal end 10A of the airtight casing 10 is airtightly sealed by a cover glass 108, and a proximal end 10B of the airtight casing 10 is airtightly sealed by a partition wall part 120. The airtight casing 10 is constituted of a first tubular body 12 and a second tubular body 14, and the second tubular body 14 is disposed in a nested shape with respect to the first tubular body 12. During the connection between the proximal ends of the first signal lines 116 and the terminal part 118, the second tubular body 14 is advanced toward the first tubular body 12.
