A solid state light source device and a dimming circuit are provided. The dimming circuit includes a rectifier circuit, a switch unit, and a control unit. The rectifier circuit is configured to convert an AC voltage signal to a rectified voltage signal. The switch unit is electrically connected between the rectifier circuit and a lighting module and configured to undergo switching according to a pulse width modulation signal to connect or disconnect the rectifier circuit and the lighting module. The control unit is electrically connected to the switch unit and configured to generate the pulse width modulation signal to control the switch unit.