A photodetector comprising: (K x M x N) photodiodes PD k,m,n (K being an integer of no less than 2; k being integers of no less than 1 and no more than K; M being an integer of no less than 1; m being integers of no less than 1 and no more than M; N being an integer of no less than 2; and n being integers of no less than 1 and no more than N), each generating an electric charge by an amount corresponding to an intensity of light incident thereon; (M x N) integrating circuits, one of each being provided in correspondence to K photodiodes PD k,m,n (k = 1 to K) among the (K x M x N) photodiodes PD k,m,n and each successively inputting and accumulating the electric charges generated at the K photodiodes PD k,m,n (k = 1 to K) and outputting a voltage that is in accordance with the amount of the accumulated electric charges; A/D converting circuits, each A/D converting circuit being provided in correspondence to one of said (M x N) integrating circuits, and outputting a digital value according to the voltage outputted from the corresponding integrated circuit; wherein the (K x M x N) photodiodes PD k,m,n are arranged in M rows and (K x N) columns either two-dimensionally (when M=2) or one-dimensionally (when M=1), with each photodiode PD k,m,n being positioned at the position of the m-th row and (n+(k-1)N)-th column; switches SW k,m,n are provided in a one-to-one correspondence with respect to photodiodes PD k,m,n and are arranged between the photodiodes PD k,m,n and signal lines SL m,n; each set of K photodiodes PD k,m,n (k=1 to K) is connected via the corresponding switches SW k,m,n to a signal line SL m,n; each signal line SL m,n is connected to an input end of an integrated circuit; and switches SW k,m,n on each column are connected to the same control line CL k,n and the opening/closing of each column of switches SW k,m,n is controlled together by a control signal that is transmitted via the control line CL k,n, wherein switches SW k,m,n having the same m and n values are connected to the same integrated circuit. (K x M x N) photodiodes PD k,m,n (K being an integer of no less than 2; k being integers of no less than 1 and no more than K; M being an integer of no less than 1; m being integers of no less than 1 and no more than M; N being an integer of no less than 2; and n being integers of no less than 1 and no more than N), each generating an electric charge by an amount corresponding to an intensity of light incident thereon; (M x N) integrating circuits, one of each being provided in correspondence to K photodiodes PD k,m,n (k = 1 to K) among the (K x M x N) photodiodes PD k,m,n and each successively inputting and accumulating the electric charges generated at the K photodiodes PD k,m,n (k = 1 to K) and outputting a voltage that is in accordance with the amount of the accumulated electric charges; A/D converting circuits, each A/D converting circuit being provided in correspondence to one of said (M x N) integrating circuits, and outputting a digital value according to the voltage outputted from the corresponding integrated circuit; wherein the (K x M x N) photodiodes PD k,m,n are arranged in M rows and (K x N) columns either two-dimensionally (when M=2) or one-dimensionally (when M=1), with each photodiode PD k,m,n being positioned at the position of the m-th row and (n+(k-1)N)-th column; switches SW k,m,n are provided in a one-to-one correspondence with respect to photodiodes PD k,m,n and are arranged between the photodiodes PD k,m,n and signal lines SL m,n; each set of K photodiodes PD k,m,n (k=1 to K) is connected via the corresponding switches SW k,m,n to a signal line SL m,n; each signal line SL m,n is connected to an input end of an integrated circuit; and switches SW k,m,n on each column are connected to the same control line CL k,n and the opening/closing of each column of switches SW k,m,n is controlled together by a control signal that is transmitted via the control line CL k,n, wherein switches SW k,m,n having the same m and n values are connected to the same integrated circuit.