A first thermosiphon circuit includes a first evaporator configured to cool a first target device by a latent heat of evaporation of a working fluid that absorbs a heat from the first target device, and a first passage communicating with the first evaporator. A second thermosiphon circuit includes a second evaporator configured to cool a second target device by a latent heat of evaporation of a working fluid that absorbs a heat from the second target device, and a second passage communicating with the second evaporator. A main condenser includes a first heat exchanger provided in the first passage and a second heat exchanger provided in the second passage, and is configured to allow the working fluid flowing through the first heat exchanger, the working fluid flowing through the second heat exchanger, and a predetermined cold energy supply medium to exchange heat with each other.