A filter, in particular, a finite impulse response (FIR) filter having a variable data input and output rate is disclosed. The FIR filter includes a first-in first-out (FIFO) architectural buffer, an address generator for circularly generating respective addresses for FIFO of data items and providing the addresses to the buffer, a filter for performing filtering on data items having different rates, which are input from the buffer, and outputting one or more data, and a controller for controlling address generation of the address generator and controlling transfer paths of data items for filtering of the filter. It is possible to variably control the input and output rate of filtering data by the FIR filter.