To obtain an electromagnetic flowmeter by which a flow rate can be measured with good accuracy irrespective of whether the distribution of a flow velocity is symmetric with respect to an axis or not by providing an adjusting member which adjusts the gap between a conduit and an inner core and by which the distribution of a magnetic field inside the conduit is adjusted freely.

An inner core 11 is molded by a magnetic material, and it is installed between a core 3, an exciting coil 4 and a measuring pipe 1 so as to generate a magnetic field which is perpendicular to the length direction of the measuring pipe 1. Variable screws 12 are installed at four corners of the inner core 11. By adjusting the variable screws 12, the gap between the measuring pipe 1 and the inner core 11 is adjusted, and the distribution of the magnetic field inside the measuring pipe 1 can be adjusted freely. Consequently, a magnetic flux density near measuring electrodes 5 can be made larger than a magnetic flux density in the central part of the measuring pipe 1, and the magnetic flux density inside the measuring pipe 1 can be made uniform. Even after an assembling operation, a flow rate can be measured with good accuracy irrespective of whether the distribution of a flow velocity is symmetric with respect to an axis or not.