To provide an inexpensive crime prevention system capable of efficiently preventing, for example, peeping during bathing, and capable of saving power.

A outdoor water heater 27 is connected to an indoor remote controller 1 via a communication line 2. The water heater 27 has a human detection sensor 7 for detecting a person who is near the water heater 27. When the human detection sensor 7 detects the person, a signal for indicating that the person is detected is outputted from the human detection sensor 7. The outputted signal is transmitted from the water heater 27 to the remote controller 1 via the communication line 2, and information for indicating the detection of the person is informed by voice and display by a reporting means provided in the remote controller 1. An automatic switch 36 is provided in the remote controller 1 for turning on and off automatic hot water filling operation in the water heater 27. When the automatic switch 36 is turned on and off, the human detection sensor 7 is set to operation and non-operation modes, respectively.