To provide a videoclock signal generator which generates a videoclock signal which does not generate a distortion in a formed image.

The video clock generator comprises: a scanner (23) which scans a luminous flux; a linear scale (27) arranged in the optical path of the luminous flux; and a photodetector (31) which receives the luminous flux and outputs an electric signal by optoelectronic transduction. The video clock generator further comprises: a differentiating circuit (103) which outputs the differentiation signal of the electric signal; a first comparator (105) which binarizes the differentiation signal and outputs a binarized pulse; a second comparator (115) which binarizes the electric signal and outputs a binarized pulse; a first edge detector (109) which detects the edge of the pulse from the first comparator and outputs a first edge signal; a second edge detector (117) which detects the edge of the pulse from the second comparator and outputs a second edge signal; and a synthesizing circuit (119) which synthesizes the first and the second edge signals and generates a videoclock.