According to an embodiment, a light beam scanner includes a first mirror and an angular magnification unit. The first mirror makes a normal direction of a reflecting surface change repeatedly. The angular magnification unit is configured to return, when viewed from a first direction, reflected light from the first mirror to the first mirror so that light is reflected at substantially the same points on the first mirror for a plural number of times, and increase, when viewed from the first direction, an angle each time light is reflected from the first mirror, the angle being between the normal direction of the reflecting surface and a reflection direction of light. Light is emitted from the angular magnification unit after the light is reflected from the first mirror for a predetermined number of times.