In a facility management system, a controller that constitutes an information acquisition device attached to a signal light includes: a flashing detection operation execution section that executes flashing detection operation in which first cyclic operation is repeatedly performed a plurality of times consecutively, the first cyclic operation being defined as operation constituted of predetermined sampling operation to acquire light emission information through a sensor and first quiescent operation performed subsequent to the sampling operation, and having a cycle corresponding to a flashing cycle of the signal lamp, and a continuation processing section that repeats second cyclic operation a plurality of times consecutively, the second cyclic operation being defined as operation constituted of the flashing detection operation and second quiescent operation performed subsequent to the flashing detection operation and having a time that is longer than a time of the first quiescent operation.