An object of the present invention is to provide a simple biochemical sensor making use of the light interference effect of an optical film which is capable of measuring binding of biochemical substances at a high throughput. In the present invention, a solution containing samples 18 is passed through the sensor having probes 17 provided on an optical film with a refractive index of not less than 1.8 and not greater than 3 on a substrate, and binding of the probes 17 and samples 18 is detected from the change of intensity of the reflected light. This makes it possible to measure binding of biochemical substances at a high throughput with high precision.