Matrix metalloproteinase (MMP) is known to be involved in chronic inflammation, tumor invasion, and carcinogenesis. To detect MMP-2, we examined the use of field effect transistors (FETs). After the addition of MMP-2 to a fibronectin (FN)-immobilized gate, negative value of FET response was observed, which indicates MMP-2 decreased the amount of negative charges arising from FN molecules. This FET device successfully detected MMP-2 by utilizing degradation of FN on the gate.