A light source device, including: a high pressure discharge lamp in which an electric discharge is generated between a pair of electrodes; a lighting device that supplies drive current having a predetermined frequency to the high pressure discharge lamp to light and drive the high pressure discharge lamp; and a control device that controllably drives the lighting device, the control device including: a power-change controller that controls drive power supplied from the lighting device to the high pressure discharge lamp to be changeable at least between a first power and a second power lower than the first power; and a frequency-change controller that controls a frequency of the drive current supplied from the lighting device to the high pressure discharge lamp to be changeable, in a second power drive mode in which the second power is supplied to the high pressure discharge lamp by the power-change controller, the frequency-change controller changing the frequency of the drive power to a frequency higher than a frequency in a first drive mode in which the first power is supplied to the high pressure discharge lamp by the power-change controller.