An optical image measurement device, comprising: a light source adapted to generate a laser beam; a light amount adjustment part adapted to adjust said light amount of the laser beam generated by said light source; a scanning part adapted to scan said laser beam on a measured object by changing the irradiation position of said laser beam on said measured object by changing the direction of a galvanomirror; a detection part adapted to detect said laser beam reflected by said measured object; an image formation part adapted to form an image of said measured object based on the detection result obtained by said detection part; a light amount measuring part that is placed outside the light path of said laser beam irradiated on said measured object and is capable of measuring the light amount; and a mode switching part adapted to alternatively switch between two modes: an image formation mode for forming an image of said measured object and a light amount measurement mode for measuring the light amount of said laser beam; said scanning part, said light amount measuring part and said light amount adjustment part further being adapted so that when the mode is switched to said light amount measurement mode by said mode switching part, said scanning part changes the direction of said galvanomirror to input said laser beam to said light amount measuring part; said light amount measuring part measures the light amount of said input laser beam; and said light amount adjustment part adjusts the light amount of the laser beam generated by said light source such that the light amount measured by the said light amount measuring part falls within a previously stored specified light amount range. a light source adapted to generate a laser beam; a light amount adjustment part adapted to adjust said light amount of the laser beam generated by said light source; a scanning part adapted to scan said laser beam on a measured object by changing the irradiation position of said laser beam on said measured object by changing the direction of a galvanomirror; a detection part adapted to detect said laser beam reflected by said measured object; an image formation part adapted to form an image of said measured object based on the detection result obtained by said detection part; a light amount measuring part that is placed outside the light path of said laser beam irradiated on said measured object and is capable of measuring the light amount; and a mode switching part adapted to alternatively switch between two modes: an image formation mode for forming an image of said measured object and a light amount measurement mode for measuring the light amount of said laser beam; said scanning part, said light amount measuring part and said light amount adjustment part further being adapted so that when the mode is switched to said light amount measurement mode by said mode switching part, said scanning part changes the direction of said galvanomirror to input said laser beam to said light amount measuring part; said light amount measuring part measures the light amount of said input laser beam; and said light amount adjustment part adjusts the light amount of the laser beam generated by said light source such that the light amount measured by the said light amount measuring part falls within a previously stored specified light amount range.