An oscillator includes an oscillator circuit, a crystal filter, a package portion, and a heating portion. The oscillator circuit is configured to output an oscillation signal. The crystal filter has a frequency characteristic where an attenuation at a detuned frequency is larger than an attenuation at an oscillation frequency of the oscillation signal. The detuned frequency is a frequency different from the oscillation frequency. The package portion covers a crystal blank of the oscillator circuit and a crystal blank of the crystal filter. The heating portion is configured to heat the crystal blank of the oscillator circuit and the crystal blank of the crystal filter using a resistor disposed between: a wiring board to which the package portion is secured, and the package portion.