An optical ranging sensor includes an infrared LED encapsulated in a first light-permeable resin section, a light receiving device encapsulated in a second light-permeable resin section, a light-shielding resin member in contact with the first and second resin sections, a drive circuit section for driving the LED, a light receiving device control section for controlling the light receiving device, and a control section for the drive circuit section and light receiving device control section. Under control of the control section, a driving time of the LED coincides with an exposure time of the light receiving device. Further, while the LED is not driven, the light receiving device is also exposed for a time identical to the exposure time. An output difference between outputs at the exposure with driving the LED and at the exposure without driving the LED is calculated, and ranging is performed based on the output difference.