A processing-in-memory (PIM) device includes a multiplication/accumulation (MAC) operator. The MAC operator includes a multiplying block and an adding block. The multiplying block includes a first multiplier and a second multiplier. The first multiplier performs a first multiplying calculation of first half data of first data and first half data of second data. The second multiplier performs a second multiplying calculation of second half data of the first data and second half data of the second data. The adding block performs an adding calculation of first multiplication result data outputted from the first multiplier and second multiplication result data outputted from the second multiplier. The MAC operator receives a test mode signal having a first level to perform a test operation for the multiplying block.