A magnetic field application device applying a magnetic field to a magnetocaloric material includes: a magnetic field generating component; a first yoke connected to both poles of the magnetic field generating component; and a second yoke movably disposed between a first position and a second position. A first closed magnetic circuit formed by the magnetic field generating component and the first yoke passes through a magnetic field application region in which the magnetocaloric material is accommodated. A second closed magnetic circuit formed by the magnetic field generating component, the first yoke, and the second yoke bypasses the magnetic field application region. Magnetic resistance of the second closed magnetic circuit when the second yoke is located at the second position is smaller than the magnetic resistance of the second closed magnetic circuit when the second yoke is located at the first position.