A laser device includes a light source that radiates a laser beam having one or more frequencies, and a nonlinear optical medium on which the laser beam is incident, the non-linear optical medium including at least one dispersive medium that is transparent and arranged along a direction in which the laser beam is radiated. The nonlinear optical medium drives a nonlinear optical process including generation of laser beams having different frequencies. The at least one dispersive medium has an effective thickness that causes a relative phase relationship among all the laser beams relevant to the nonlinear optical process to approximately satisfy a predetermined value.