An endoscope includes an insert section, a CCD is mounted at the end of the insert section, and a CCU for producing a video signal is arranged in a control unit connected to a proximal end of the insert unit. The CCU includes a general-purpose DSP board having the function of producing a standard video signal, and a function adjustment/expansion circuit board for correcting a signal delay due to the length of a signal line connected to the CCD. The DSP boards and the function adjustment/expansion circuit boards, respectively remaining the same in circuit arrangement, are used for a plurality of types of endoscopes having insert sections having different insertion lengths.