A vibrator that is capable of vibrating without using an electrode and has good detection sensitivity is provided. A carbon-based material vibrator for vibration by light irradiation has a biological substance or a substance capable of identifying a biological substance immobilized on the vibrator. The vibrator may not include a counter electrode for applying a voltage to the vibrator. The carbon-based material may be graphite. A thermal conductivity λ1 in a plane direction of the carbon-based material is 100 times or more than a thermal conductivity λ2 in a thickness direction of the carbon-based material.