A light source device includes at least one light emitting diode, at least one dichroic mirror, a condenser, and a fly's eye device. The light emitting diode is operable to generate at least one kind of light. The dichroic mirror is disposed corresponding to the light emitting diode to combine the light into an optical path when the light passes through the dichroic mirror. The condenser is disposed corresponding to the dichroic mirror to gather the light when the light passes through the condenser. The fly's eye device is disposed corresponding to the condenser to homogenize the light when the light passes through the fly's eye device. Furthermore, a projection device is disclosed herein.