The invention provides a laser scanner, which comprises a light source unit, a light receiving unit, a distance measuring unit, an angle measuring unit, a telescope unit capable of rotating in a horizontal direction and a vertical direction, a rotation driving unit, a directional angle detector, and a control arithmetic unit, wherein the light source unit is an MOPA type and has an oscillator control circuit, a main oscillator, and an optical amplifier, wherein the oscillator control circuit has a repetition frequency setting component, a pulse peak output setting component, a pulse width setting component and an amplification factor calculating component and oscillates the main oscillator corresponding to a measured distance, and wherein the amplification factor calculating component calculates an amplification factor based on a repetition frequency, a pulse peak output, and a pulse width and amplifies the optical amplifier based on a calculated amplification factor.