To provide a light source device capable of preventing an optical axis of a convergence type discharge lamp from being shifted when replacing a lamp.

The light source device 1 includes a device body 4 built in replaceably with the convergence type discharge lamp 44, and outputs a light from a base 6 provided in the device body 4. The light source device 1 includes a lamp attaching block 50 for holding the convergence type discharge lamp 44 to be attachable and detachable. The lamp attaching block 50 includes: a pedestal 52 formed with a U-shaped cut-out for receiving a neck part 61A of the convergence type discharge lamp 44; and a plate-like front plate 54 forming a face perpendicular to an optical axis K, on which a flange part 62A of a convergence type reflecting mirror 62 of the convergence type discharge lamp 44 abuts. The lamp attaching block further includes: a presser part 57 for pressing the neck part 61A received by the pedestal 52; and a presser spring 56 for biasing the convergence type discharge lamp 44 toward the front plate 54, to bring the flange part 62A into tight contact.