1. An event detecting method of an image monitoring device, the method comprising: setting first and second monitoring events related to a monitored image; obtaining a monitored image; detecting an occurrence of a first monitoring event with respect to an object from the obtained monitored image; detecting an occurrence of a second monitoring event with respect to the object from the obtained monitored image when the first monitoring event occurs; and storing information regarding the detected occurrence of the second monitoring event, wherein the setting the first and second monitoring events comprises: setting at least one of a position in which a first region corresponding to the first monitoring event is set, a size of the first region, and a shape of the first region based on a user input, wherein the first monitoring event occurs within the first region; setting at least one of a position in which a second region corresponding to the second monitoring event is set, a size of the second region, and a shape of the second region based on a user input, wherein the second monitoring event occurs within the second region; inputting sequence information with respect to the first and second monitoring events; determining the first and second monitoring events based on the sequence information; and setting a duration time between the first and second monitoring events, wherein the information is stored only if the occurrence of the second monitoring event is detected after a lapse of the duration time from the occurrence of the first monitoring event.