The present disclosure relates to a multi-channel detector having a reduced number of output channels and including: a linear amplifier linearly amplifying an input signal; an offset correcting unit configured by a circuit that is independent from the linear amplifier, including an operational amplifier inside, and correcting an offset level that changes in accordance with an amplification rate of the operational amplifier; a uniformity correcting unit reducing a non-uniform characteristic of the input signal by finely adjusting a gain of an output signal of the linear amplifier; a signal delay unit delaying an output signal of the uniformity correcting unit until a time point when output signals are generated from a comparison unit and a signal determining unit, and a switch circuit receives a trigger from the signal determining unit; a comparison unit comparing the output signal of the uniformity correcting unit with a signal of a predetermined level with each other; a signal determining unit receiving a trigger signal from the comparison unit, determining channel position information of a channel in which an event occurs, transmitting a trigger signal to a switch circuit located at the determined channel position, and outputting the determined position information; and a channel information processing unit receiving energy information, time information, or the channel position information of a channel in which an event occurs as input when a trigger signal is input from the signal determining unit to the switch circuit located at the determined channel position.