A new label-free biosensing platform is proposed based on a metal insulator metal (MINI) structure. This platform allows us to perform biosensing by a simple reflectivity measurement at normal incidence illumination without using any bulky optical setup. Theoretical calculation was made to find optimized M I M structural parameters, and experimental results on the label-free biosensing using the M I M platform are presented. This platform has greater sensitivity and mass resolution with respect to the anomalous reflection method, which is a label-free biosensing platform previously proposed by us. Hence, it is suitable for high throughput analysis of biomolecular detection in a microarray format.