To provide a digital channelizer and a process which divide an input band width into at least a part of N channels.

A digital channelizer 100 includes an analog/digital converter 14 which encodes the input band width to a serial digital data stream of data words, a demultiplexer 16 which is coupled with the analog/digital converter and divides the serial digital data stream into parallel data streams of data words, a window presum part 102 which is a window presum part having N outputs which are coupled to parallel data streams and are window presum functions and functions of data words from plural parallel data streams, and a discrete Fourier transform device 26' which has N inputs coupled to N outputs of the window presum part and subjects N inputs to discrete Fourier transform to generate at least a partial output of N channels.