[en] A calorimeter for absolute measurement of heat capacity of superconductors in the temperature range of 2-40 K in magnetic fields of up to 20 T designed for operation both in laboratory superconducting solenoids and in the KS-250 combined magnetic system has been developed. Heat capacity of 0.5-10 g specimens is measured by a quasidiabatic method with discrete heat intake. Discontinued heat contact is accomplished with heat-exchange gas pumped-out with an inner sorption pump. Temperature is measured with a carbon resistance thermometer, correction for its resistance change an a magnetic field considering. Working volume of the calorimeter is surrounded with a high-pure aluminium screen cooled to helium temperature, which ensures considerable weakening of magnetic field pulsations and decreases undesirable heating of a specimen with Foucault currents. Heat capacity of pure copper specimen was measured and measurement error was evaluated, which doesn't exceed 1% when operating in a superconducting solenoid and 2% when operating in the combined magnetic system. Results of measurements of V³Ga superconductor heat capacity in magnetic fields of up to 20 T are given