The invention provides a sample fixing device used for testing hardness, and is characterized by comprising a metal casing and a magnetic field generation pedestal which have same shape and coupled size, the magnetic field generation pedestal is positioned below the metal casing, the magnetic field generation pedestal is connected to dc source to generate a magnetic field; a cavity is provided in the metal casing, the magnetic field induction particles are filled in the cavity, the magnetic field induction particles mutually generate suction under magnetic field effect, thereby the sample in the magnetic field induction particles can be fixed, and the surface to be measured keeps a horizontal state. The sample fixing device used for testing hardness is suitable for hardness samples with a plurality of sizes and shapes, the operation is simple, the work state is stable, the test result has high repeatability, and the sample fixing device is suitable for fixing the measure samples such as Brinell, Vickers and Rockwell hardometers.