A detector comprising: a wiring board; a plurality of semiconductor chips arranged on the wiring board while being two-dimensionally separated from each other; and first and second bump electrodes (BE, B2) arranged between each of the semiconductor chips and the wiring board; wherein each of the semiconductor chips comprises: a semiconductor substrate having a plurality of photodetector units arranged two-dimensionally; an insulating layer formed on a front face of the semiconductor substrate; a common electrode arranged on the insulating layer; a readout line (3C, TL) for electrically connecting a quenching resistance of each of the photodetector units and the common electrode to each other; and a through electrode extending from the common electrode to a rear face of the semiconductor substrate through a through hole of the semiconductor substrate; wherein a respective glass sheet is bonded to each semiconductor chip and wherein the respective glass sheets are separated from each other; wherein each of the photodetector units comprises: an avalanche photodiode, i.e. APD, having a first semiconductor region of a first conduction type and a second semiconductor region of a second conduction type for constructing a p-n junction with the first semiconductor region and outputting a carrier; and the quenching resistance electrically connected to the second semiconductor region of the APD; wherein the first bump electrode electrically connects the through electrode and the wiring board to each other; and wherein the second bump electrode electrically connects the first semiconductor region of the APD and the wiring board to each other. a wiring board; a plurality of semiconductor chips arranged on the wiring board while being two-dimensionally separated from each other; and first and second bump electrodes (BE, B2) arranged between each of the semiconductor chips and the wiring board; wherein each of the semiconductor chips comprises: a semiconductor substrate having a plurality of photodetector units arranged two-dimensionally; an insulating layer formed on a front face of the semiconductor substrate; a common electrode arranged on the insulating layer; a readout line (3C, TL) for electrically connecting a quenching resistance of each of the photodetector units and the common electrode to each other; and a through electrode extending from the common electrode to a rear face of the semiconductor substrate through a through hole of the semiconductor substrate; wherein a respective glass sheet is bonded to each semiconductor chip and wherein the respective glass sheets are separated from each other; wherein each of the photodetector units comprises: an avalanche photodiode, i.e. APD, having a first semiconductor region of a first conduction type and a second semiconductor region of a second conduction type for constructing a p-n junction with the first semiconductor region and outputting a carrier; and the quenching resistance electrically connected to the second semiconductor region of the APD; wherein the first bump electrode electrically connects the through electrode and the wiring board to each other; and wherein the second bump electrode electrically connects the first semiconductor region of the APD and the wiring board to each other. an avalanche photodiode, i.e. APD, having a first semiconductor region of a first conduction type and a second semiconductor region of a second conduction type for constructing a p-n junction with the first semiconductor region and outputting a carrier; and the quenching resistance electrically connected to the second semiconductor region of the APD; wherein the first bump electrode electrically connects the through electrode and the wiring board to each other; and wherein the second bump electrode electrically connects the first semiconductor region of the APD and the wiring board to each other.