A semiconductor light detection element has a plurality of channels, each of which consists of a photodiode array including a plurality of avalanche photodiodes operating in Geiger mode, quenching resistors connected in series to the respective avalanche photodiodes, and signal lines to which the quenching resistors are connected in parallel. A mounting substrate is configured so that a plurality of electrodes corresponding to the respective channels are arranged on a third principal surface side and so that a signal processing unit for processing output signals from the respective channels is arranged on a fourth principal surface side. In a semiconductor substrate, through-hole electrodes electrically connected to the signal lines are formed for the respective channels. The through-hole electrodes and the electrodes are electrically connected through bump electrodes.