A MEMS resonator 100 including a substrate 112; an vibrator 102 including an mechanically vibrating part and a fixed part; at least one electrode 108 that is close to the vibrator and has an area overlapping with the vibrator across a gap 109 in a direction perpendicular to a surface of the substrate; and a pressure transferring mechanism to displace the at least one electrode according to an externally applied pressure so as to change the gap; is connected to a detection circuit that detects transmission characteristics of an AC signal from an input electrode to an output electrode, the input and output electrodes being one and the other of the vibrator 102 and the at least one electrode 108, and the pressure is detected based on the transmission characteristics of the AC signal that is detected by the detection circuit.