The conservator is provided with a housing (110) that houses an insulation oil (130), a rubber bag (120) that inflates or deflates inside the housing (110) so as to contact an oil surface of the insulation oil (130), and an oil level gauge that detects the oil level of the insulation oil (130) housed inside the housing (110). The oil level gauge includes a float member (140), an arm (150) connected to one end of the float member (140), and a dial display unit (160) that displays an oil level in response to an angle of the arm (150). The float member (140) is swingably connected to the arm (150), extending away from the arm (150) along the lower surface of the rubber bag (120). The length of the float member (140) in the extending direction thereof is larger than the maximum thickness of the float member (140).