A laser apparatus is disclosed. The laser apparatus has a diffraction grating that receives laser light from a semiconductor laser, emits first order diffracted light having a predetermined wavelength to the semiconductor laser, and reflects zero-th order light, a reflection section that reflects the zero-th order light reflected by the diffraction grating, a hold section that holds the diffraction grating and the reflection section while an open angle of the diffraction grating and the reflection section is kept constant, the hold section being rotatable with a fulcrum of an intersection of an extended line of a front surface of the diffraction grating and an extended line of a front surface of the reflection section, and a linear drive section that rotates the hold section with a linear motion of a piezoelectric device that expands and shrinks by the piezoelectric effect.