An oscillator includes: a plurality of MEMS vibrators each having a first terminal and a second terminal, and having respective resonant frequencies different from each other; an amplifier circuit having an input terminal and an output terminal; a connection circuit adapted to connect the first terminal of one of the MEMS vibrators and the input terminal to each other, and the second terminal of the one of the MEMS vibrators and the output terminal to each other; a signal reception terminal adapted to receive a switching signal used to switch a state of the connection circuit; and a switching circuit adapted to make the connection circuit switch the MEMS vibrator to be connected to the amplifier circuit based on the switching signal, wherein the MEMS vibrators are housed in an inside of a cavity, and the signal reception terminal is disposed outside the cavity.