According to one embodiment, in one embodiment of the invention, a laser drive circuit is provided with a first current source, a second drive current source, and a third current source. The control section selectively obtains a plurality of laser light use mode of controlling the from first to third current sources to use pulse laser light accompanying relaxation oscillation, and a complex laser light use mode of using laser light where laser pulses are combined, whose starting end has an abrupt impulse change portion caused by relaxation oscillation and whose intermediate section is a flat portion with a fixed intensity.