A light source device comprising: a wavelength conversion member including at least a phosphor, and configured to convert excitation light in an excitation wavelength band into first light in a first wavelength band different from the excitation wavelength band; a first light source section configured to emit the excitation light; a second light source section configured to emit second light in a second wavelength band different from the first wavelength band; and a color combining element configured to combine the first light and the second light with each other to form composite light and emit the composite light, the color combining element being formed of a dichroic prism having a dichroic mirror disposed inside, wherein the wavelength conversion member has a first end surface and a second end surface opposed to each other, wherein the wavelength conversion member has a side surface crossing the first end surface and the second end surface, wherein a dimension of the wavelength conversion member in a normal direction of the first end surface is longer than a dimension of the wavelength conversion member in a normal direction of the side surface, wherein the first light source section is configured such that, in use, the excitation light enters the wavelength conversion member from the side surface, and wherein the wavelength conversion member is configured such that, in use, the first light is emitted from the first end surface; characterized in that the color combining element has a first surface and a second surface opposed to each other, and a third surface crossing the first surface and the second surface, wherein an area of the second surface is larger than an area of the first surface; the light source device is configured such that, in use, the first light emitted from the wavelength conversion member enters the color combining element from the first surface, the second light emitted from the second light source section enters the color combining element from the third surface, and the composite light is emitted from the second surface; and the color combining element has an angle conversion function of making a diffusion angle in the second surface smaller than a diffusion angle in the first surface. a wavelength conversion member including at least a phosphor, and configured to convert excitation light in an excitation wavelength band into first light in a first wavelength band different from the excitation wavelength band; a first light source section configured to emit the excitation light; a second light source section configured to emit second light in a second wavelength band different from the first wavelength band; and a color combining element configured to combine the first light and the second light with each other to form composite light and emit the composite light, the color combining element being formed of a dichroic prism having a dichroic mirror disposed inside, wherein the wavelength conversion member has a first end surface and a second end surface opposed to each other, wherein the wavelength conversion member has a side surface crossing the first end surface and the second end surface, wherein a dimension of the wavelength conversion member in a normal direction of the first end surface is longer than a dimension of the wavelength conversion member in a normal direction of the side surface, wherein the first light source section is configured such that, in use, the excitation light enters the wavelength conversion member from the side surface, and wherein the wavelength conversion member is configured such that, in use, the first light is emitted from the first end surface; characterized in that the color combining element has a first surface and a second surface opposed to each other, and a third surface crossing the first surface and the second surface, wherein an area of the second surface is larger than an area of the first surface; the light source device is configured such that, in use, the first light emitted from the wavelength conversion member enters the color combining element from the first surface, the second light emitted from the second light source section enters the color combining element from the third surface, and the composite light is emitted from the second surface; and the first light emitted from the wavelength conversion member enters the color combining element from the first surface, the second light emitted from the second light source section enters the color combining element from the third surface, and the composite light is emitted from the second surface; and the color combining element has an angle conversion function of making a diffusion angle in the second surface smaller than a diffusion angle in the first surface.