In a monitoring apparatus, a target-object to be monitored is observed by an observing unit and a countermeasure is applied depending on an observed situation. The knowledge and information on the general feature relating to the target-object, the observing method and the countermeasure method are prepared in the storing unit of the monitoring apparatus. The individual knowledge and information relating to the target-object are registered by the user in the storing unit by utilizing the general monitor-knowledge. In the monitor-plan executing unit, the observing method and the countermeasure method of the target-object are planned in accordance with the situation by utilizing the general monitor-knowledge and the individual monitor-knowledge, and the plan is executed.