An information processing unit including a general-purpose personal computer (200) and a sequence engine (300) having a ladder interpreter (301) connected to the general-purpose personal computer (200) through an expansion bus (500). The ladder interpreter (301) executes a sequence command on the basis of a predetermined sequence program requested by the general-purpose personal computer (200), and the general-purpose personal computer (200) executes information processing on the basis of a predetermined information processing program and peripheral processing in accordance with a peripheral processing request from the ladder interpreter (301).