To provide a laser semi-active guide system in which a guide signal can be obtained by a digital processing for simply determining presence of a laser reflection light.

A laser reflection light from a target is collected by an optical system 2 through a dome 1 and only a laser light irradiated from a laser irradiator is focused on a two-dimensional array sensor 4 by an interference filter 3. Output of each pixel from the two-dimensional array sensor 4 is amplified by a preamplifier and the value thereof is held in a hold circuit 6 during a time required for reading out the two-dimensional array sensor entirely. Subsequently, each output from the hold circuit 6 is switched at a switching section 8 by a switching signal from a signal processing section 9 before being inputted thereto and producing two-dimensional data. A guide signal is generated in the signal processing section 9 based on the two-dimensional data. Spatial stabilization is performed by controlling a ginbal drive section 10 and a jinbal mechanism section 7 using the generated guide signal and a target is tracked.