Affinity Capture-Mass Spectroscopy, an analytical technique which couples the sensitivity of a label-free binding detected biosensor, and the information richness of mass spectroscopy is described. The first and second cases are provided with first and second projections on inner surfaces of the first and second cases. Therefore, the corners of the case members can be prevented from bending or deforming, and the mechanical strength of the main surface can be improved. In a preferred embodiment, a control circuit is provided that, during a writing operation, supplies data to be written to the memory cell to the bit line, supplies a pulse signal to the precharge line, and activates the word line.