A switching filter is provided in a light source device. The switching filter has a first dichroic filter which transmits illumination light in a first wavelength band from a lamp and a fluorescence observation filter which transmits at least illumination light in a second wavelength band and is rotatably provided such that the first dichroic filter and the fluorescence observation filter pass through an illumination light optical axis. An LED portion has a blue LED which emits illumination light in the first wavelength band toward the switching filter. A second dichroic filter capable of transmitting illumination light from the lamp and reflecting illumination light from the LED portion to a condenser lens is also arranged at the switching filter.