Abstract: In a pump control device (1, 1?) comprising a casing (2, 3; 2?, 3?) and a speed controller (20), in particular a frequency converter, arranged in the casing for controlling the rotational speed of an electric drive motor (103; 103?) of a fluid pump (100; 100?), the casing includes a section (3; 3?) of good thermal conductivity in which a cavity (4; 4?) is formed which exhibits connections (5, 6, 7; 5?, 6?) for coupling with the output (102; 102?) of a fluid pump (100; 100?) to be controlled by the pump control device and with pipes so that the cavity (4; 4?) can be passed through by the entire fluid stream delivered by the fluid pump, wherein the speed controller (20) is connected in a heat-conducting manner to the casing portion (3; 3?) of good thermal conductivity.