A non-contact type displacement sensor includes a light source that emits measurement light; a liquid lens apparatus in which a refractive index periodically changes in response to an input drive signal; an objective lens emitting, at a measurable object, the measurement light that is emitted from the light source and has passed through the liquid lens apparatus; a photodetector receiving the measurement light that is reflected by the measurable object and outputs a photodetection signal; and a signal processor (controller) that calculates focus timing with which the measurement light is in focus on a surface of the measurable object based on the photodetection signal output from the photodetector, and that obtains a position of the measurable object based on a phase of the focus timing with respect to a cycle of the drive signal.