A heating device includes an illuminating unit that applies laser light towards a strip-like illumination area formed along a direction crossing a direction of movement of a recording medium; and a reflecting member that surrounds the illumination area, the reflecting member reflecting again reflected light from the illumination area. The reflecting member has protruding reflecting surfaces that protrude continuously towards the recording medium along a widthwise direction crossing a longitudinal direction of the illumination area, the protruding reflecting surfaces being disposed side by side in the longitudinal direction of the illumination area. The protruding reflecting surfaces are positioned at substantially equal distances from the illumination area along the widthwise direction of the illumination area, and changed so that an entire or a portion of a cross-sectional shape along the longitudinal direction of the illumination area is curved or inclined.