In an optical beam scanning apparatus and an image forming apparatus equipped with the optical beam scanning apparatus of the present invention, a holder base is screwed to an optical housing, a holder holds a light source, and a laser drive board is screwed to the holder. Rotary adjustment of the holder about the optical axis of the light source is performed with respect to the holder base, and the holder is fixed to the holder base. According to the optical beam scanning apparatus and the image forming apparatus equipped with the optical beam scanning apparatus of the present invention, it is possible to perform rotary adjustment of the light source about the optical axis with ease even in a small space.