To provide a watt-hour meter which eliminates problems such as faulty contact and allows only a measuring part to be replaced safely and easily by ensuring the connection between the measuring part and a terminal part and enlarging the contact area of connecting terminals of the two parts.

The watt-hour meter comprises the terminal part which is provided with a row of external connecting terminals and arranges first connecting terminals each of which is electrically communicated with each of the external connecting terminals on its outer surface and the measuring part which arranges second connecting terminals each of which pairs up with each of the first connecting terminals on its outer surface. The measuring part is detachably coupled to the terminal part. On coupling, the first connecting terminals and the second connecting terminals are brought into contact with each other through their in-phase surfaces, allowing the two parts to be energized. The measuring part may be detachably coupled to the terminal part by sliding it backward and forward. For that purpose, a pair of guide means are provided in the two parts, wherein the guide means can be the first connecting terminals and the second connecting terminals.