APD SENSOR AND RANGING SYSTEM

Provided are an avalanche photodiode (APD) sensor and a ranging system capable of counting, with high accuracy, a value relating to signals from a plurality of pixels with one counter. The APD according to the present disclosure includes a plurality of pixels each including an APD, a plurality of state detection circuits configured to detect states of a plurality of first signals output from the plurality of pixels and generate a plurality of second signals including detection results of the states of the plurality of first signals, a logical operation circuit configured to perform a logical operation on the plurality of second signals or a plurality of third signals that varies in a manner that depends on the plurality of second signals and generate a fourth signal including a result of the logical operation, and a counter configured to count a value relating to the plurality of first signals on the basis of the fourth signal, each of the state detection circuits having an input terminal to which the fourth signal is input, and input of each of the first signals to a corresponding one of the state detection circuits being disabled on the basis of the fourth signal input to the input terminal.