There are provided a monitoring apparatus, a wireless communication system, a failure factor deciding method and a program which enable a user to take an appropriate countermeasure for a failure factor which has occurred in a wireless communication apparatus which employs space diversity. The monitoring apparatus (1) includes an obtaining unit (12) and a deciding unit (14). The obtaining unit (12) obtains a history related to a received signal level of a first receiver (22) and a received signal level of a second receiver (24) in a predetermined period from a wireless communication apparatus (20) including the first receiver (22) and the second receiver (24). The deciding unit (14) decides a factor of a failure that has occurred in the wireless communication apparatus (20) based on the history.