A MEMS resonator includes a main movable beam, at least one sub movable beam, and at least one exciting electrode. The main movable beam is electrically insulated from a substrate and fixed to at least one fixed end, the sub movable beam is formed to extend from the main movable beam, and the exciting electrode is provided to be close to the sub movable beam. The sub movable beam is excited by an electrostatic force to oscillate by exciting the exciting electrode using an alternating-current signal, such that the MEMS resonator resonates with at least one of a fundamental resonant frequency and harmonic frequencies thereof. The resonant frequency is changed by changing at least one of number of the at least one exciting electrode and a position of the exciting electrode relative to the sub movable beam.