A distributed Bragg reflection (DBR) semiconductor laser is controlled in an image projecting apparatus. The image projecting apparatus includes the DBR semiconductor laser which is provided with a phase region and a DBR region, a light wavelength converting device for converting fundamental-wave light emitted from the DBR semiconductor laser into second harmonic wave light, an optical deflector for scanning the second harmonic wave in a one-dimensional or two-dimensional manner, and a modulating portion for modulating the DBR semiconductor laser based on an image signal. In the control method, a coefficient calculating step and a wavelength adjusting step are performed within a non-drawing time during which a drawing signal, which corresponds to the image signal, is absent. In the coefficient calculating step, at least one coefficient in a relationship between a DBR current to be injected into the DBR region and a phase current to be injected into the phase region for continuously shifting the wavelength of the fundamental-wave light is calculated. In the wavelength adjusting step, the DBR current injected into the DBR region and the phase current injected into the phase region are changed based on the relationship such that the second harmonic wave light is adjusted.