A light source unit includes a fluorescent member configured to emit, when irradiated with excitation light, fluorescence light having a wavelength different from a wavelength of the excitation light, and a controller configured to adjust a conversion efficiency from the excitation light to the fluorescence light of the fluorescent member so that a gradient T satisfies 0.35G≦T≦0.8G in a fluorescence characteristic of the fluorescent member when a horizontal axis represents a normalized light intensity of the excitation light so that a maximum light intensity of the excitation light incident on the fluorescent member is normalized to 1, and a vertical axis represents the light intensity of the fluorescence light from the fluorescence member irradiated with the normalized light intensity of the excitation light, where G represents a gradient in the fluorescence characteristic when the normalized light intensity of the excitation light is 0.3.