A variable focal length lens device includes: a variable focal length lens whose focal length cyclically changes in accordance with an inputted drive signal; an image detector configured to detect an image of a measurement target through the variable focal length lens; a pulsed light illuminator configured to emit a pulsed light to illuminate the measurement target; and an illumination controller configured to control the pulsed light illuminator so that the pulsed light is emitted twice in one cycle of the drive signal based on two detection phases corresponding to a designated focal distance of the variable focal length lens.