PURPOSE: To obtain an ordinary endoscopic image with superior operability and high resolution and to detect a private fluorescent image with high sensitivity.

CONSTITUTION: An ordinary observation image by white light is image-formed on an image pickup surface of a CCD 15 fitted in the tip of an insertion part 5 by an objective optical system 14 formed at the tip of the insertion part 5 of an endoscope 1, and converted to an electrical signal by the CCD 15, and transmitted to a signal processor 3 on a signal cable 16 inserted through the insertion part 5 and an operating part 6. The fluorescent image of viable tissue by a laser for excitation is transmitted to the operating part 6 via an image guide 18 inserted through an objective optical system 17 and the insertion part 5, and converted to the electrical signal by an electrical signal switching circuit 20 consisting of an image intensifier and the CCD via a lens 19 fitted in the operating part 6, and transmitted to the signal processor 3 on a signal cable 21.