An electroacoustic apparatus with an optical energy conversion function is provided. The electroacoustic apparatus includes an optical energy converter for converting optical energy into electrical power. The electroacoustic apparatus further includes a signal generator and a flat speaker. The signal generator receives a signal from a sound source and generates a sound signal according to the received signal. The signal generator sends the sound signal to the flat speaker, and the flat speaker makes a sound according to the sound signal. Aforementioned operations are all performed by using the electrical power generated by the optical energy converter or a power stored therein.