High-pressure techniques open exploration of functional materials in broad research fields. An established diamond anvil cell with a boron-doped diamond heater and transport measurement terminals has performed the high-pressure synthesis of a cubic Sn3S4 superconductor. X-ray diffraction and Raman spectroscopy reveal that the Sn3S4 phase is stable in the pressure range of P > 5 GPa in a decompression process. Transport measurement terminals in the diamond anvil cell detect a metallic nature and superconductivity in the synthesized Sn3S4 with a maximum onset transition temperature (Tconset) of 13.3 K at 5.6 GPa. The observed pressure-Tc relationship is consistent with that from the first-principles calculation. The observation of superconductivity in Sn3S4 opens further materials exploration under high-temperature and -pressure conditions.