A laser oscillation apparatus, comprising a laser beam emitting unit for emitting an excitation light, an optical resonance unit at least having a laser crystal and an output mirror, a nonlinear optical medium which is placed in the optical resonance unit and which generates a second harmonic from a fundamental wave oscillated by the laser crystal, and a driving means for driving the laser beam emitting unit, wherein the nonlinear optical medium is held by a nonlinear optical medium holder, and the nonlinear optical medium holder can be rotated with respect to axes of at least two directions crossing to an optical axis passing through the optical resonance unit.