A security apparatus (2) monitors movement of users carrying security controllers (3a) through (3c) into and out of a security area (50), and controls security operations. The security apparatus (2) includes a communication unit (4) for communicating with each of the security controllers (3a) through (3c) and obtaining position information on the respective security controllers (3a) through (3c), a storage unit (11) for storing a security controller monitoring table (30), and a left-controller determining section (26) for judging whether any of the security controllers (3a) through (3c) has been left within the security area (50) and determining whether setting or canceling of the security mode is commanded automatically or based on the input operations by the users.