PURPOSE: To achieve compactification and reduction in restrictions of mounting and disposition by forming the controller in double tube construction.

CONSTITUTION: An inner tube 12 provided with an iron core 13 and cavity 17 and an outer tube 14 provided with a coil 15, magnet 18 and heater 20 on the outside are installed to the main tube. An electromagnetic pump 11 is constituted by the iron core 13 and coil 15 and an electromagnetic flowmeter 16 by the cavity 17 and magnet 18, The heater 20 mounting portion is used as an economizer 19. A hydrogen meter sensor 21 consisting of a nickel diaphragm 22, millitorr gauge 23, ion pump 25, etc. is provided to the end part of the outer tube 14. Then, the liquid metal sampled to the annulus part by the electromagnet pump 11 is heated up to a constant high temperature by way of the electromagnetic flowmeter 16, economizer 19, after which it is sent to the hydrogen meter sensor 21 where it is measured of hydrogen concentration. The employment of the double tube construction eliminates the need for any piping, insulating materials and devices, etc. for connecting each constituting apparatus and enables the desired object to be achieved.