Abstract: An occupancy sensor device has a sensor and a fastener. The sensor has a body and a connector. The body has a detector and a lens. The lens covers the detector. The connector is formed on the body. The fastener is connected securely to the connector of the sensor. When the occupancy sensor device is installed on a light, the connector is mounted through a sensor hole of a light cover first, and the fastener is connected securely to the connector. Then the installation is completed and the sensor device is mounted securely on the light cover. Because the sensor has the connector directly formed on the body and the connector can be connected securely to the fastener, the sensor device is easily mounted on various kinds of lights regardless of the structure of the base.