A moving picture data compression device 1 is provided with a controller 20 for inputting a realtime/non-realtime switch signal to switchers 30 and 40 when a realtime/non-realtime switch interrupt is received from a personal computer 3 in order to control a compressor 60 to compress either realtime data recorded on a video tape 5 or non-realtime data recorded on a video file 7 according to a user's desire. When compressing non-realtime data, the controller 20 sends a synchronization signal to the compressor 60, after outputting one field worth of video signal to a buffer 50, in order to instruct the compressor 60 to read data. When the controller 20 receives a one-field read end interrupt, indicative of the end of the reading operation, from the compressor 60, the controller 20 outputs the next field data to the buffer 50.