Inconel 718 high-temperature grade alloy is usually heat treated to improve its strength characteristics. The main hardening mechanism of this superalloy is the precipitation of dispersed particles of secondary phases. Heat treatment modes differ depending on the method of manufacturing metal products. For the cast and deformed state, sufficiently studied today, the heat treatment modes were developed. For the selective laser melting (SLM) of Inconel 718, a research is ongoing to determine rational heat treatment modes. The purpose of present work is an establishing of rational modes of heat treatment of parts made of Inconel 718, manufactured using SLM technology to obtain a high complex of mechanical properties. Specimens make using the SLM technology on equipment of LLC ‘Additive Laser Technology of Ukraine’ from Inconel 718 alloy powder in the initial state and after heat treatment according to experimental modes, which differed in cooling conditions after the first high-temperature stage (in water and in air), are investigated. X-ray structural analysis is performed, as well as the mechanical properties and microstructure of samples are studied. As established, since a significant amount of the $\delta$-phase does not form during the SLM process, then after the high-temperature stage of heat treatment there is no need for accelerated cooling in water to suppress precipitation of this phase. When the precipitation of the $\delta$-phase is suppressed, the number and size of particles of the $\gamma^{''}$-phase increases, which leads to a decrease in strength indicators. Recommended heat treatment mode: heating 980°C with 1-hour exposure, cooling in air to ambient temperature, 8-hours exposure at 720°C, cooling with a furnace to 620°C, exposure at 620°C during 8 hours.