PURPOSE: To provide an inspection device in reactor which can observe the interior of fast breeder reactor with vivid feeling, can designate the photographing position/direction of an ultrasonic camera naturally, and can move easily and accurately to an intended position with minimum designation.

CONSTITUTION: Three-dimensional data from a relative azimuth detecting section 2, a view point deciding section 3, and a three-dimensional data storing section 4 are managed at a three-dimensional data managing section 5. A display screen control section 6 generates image information based on the management information and displays a three-dimensional image having vivid feeling utilizing parallax of an operator on the screen of a head attaching image display 1. Based on the results of photograph in a fast breeder reactor taken by an ultrasonic camera 7, a profile recovery section 8 recovers profile data within the photographing range and updates three-dimensional structural data stored in the three-dimensional data storing section 4. In general, positional/directional data of the ultrasonic camera 7 is inputted with the use of a three-dimensional pointing unit 10.