To control flow and speed of fluid by changing volumetric magnetic susceptibility of the fluid in magnetic field inclination.

A non-magnetic cylindrical body 2 is placed in air, and a magnetic field magnetic field strength of which decreases from one end to the other end is applied inside of the cylindrical body 2 by a coil 3 which is a magnetic field generating means. Thereafter, when a part of the air in the cylindrical body 2 is raised in temperature by a heater 4, density of the air raised in temperature decreases, and volumetric magnetic susceptibility decreases. Additionally, magnetic susceptibility of gas molecules themselves decreases by temperature rise, and it contributes to decrease of the volmetric magnetic susceptibility. As the air the volmetric magnetic susceptibility of which becomes low is pushed out to the side where magnetic field strength is low along magnetic field strength inclination, an air current from the side where magnetic field strength is high to the side where it is low is formed inside of the cylindrical body 2. In the meantime, a part of the air in the cylindrical body 2 is cooled to form an air current from the side where magnetic field strength is low to the side where it is high in the cylindrical body 2.