An internal combustion engine control device configured to control an internal combustion engine provided with a cylinder and an EGR mechanism configured to return an exhaust gas discharged from the cylinder to an intake side of the cylinder, the internal combustion engine control device comprising: an EGR control unit configured to control an EGR flow rate of the EGR mechanism; and a humidity detection unit configured to directly or indirectly detect humidity of an ambient air supplied to the cylinder, wherein the EGR control unit is configured to compute a moisture amount of the ambient air, M H2O,air, and a moisture amount of the recirculating exhaust gas, β, and is configured to control the EGR mechanism on the basis of a stable combustion limitation cylinder mass, M max,map, set depending on a combustion state of the cylinder, a mass of the air, m air, introduced into the cylinder, and a mass of fuel, M Fuel, and the moisture amount finally introduced into the cylinder, wherein the internal combustion engine further has a supercharger and a catalyst placed in a downstream side of a turbine of the supercharger, the EGR mechanism has a high-pressure EGR mechanism configured to return the exhaust gas from an outlet port in an upstream side of the turbine of the supercharger to an inlet port in a downstream side of the compressor of the supercharger and a low-pressure EGR mechanism configured to return the exhaust gas from the outlet port in a downstream side of the catalyst to the inlet port in an upstream side of the compressor of the supercharger, and the EGR control unit is configured to set the stable combustion limitation cylinder mass, M max,map, to be large when the exhaust gas is returned to the intake side of the cylinder using the high-pressure EGR mechanism, compared to a case where the exhaust gas is recirculated using the low-pressure EGR mechanism and is configured to control the exhaust gas amount, M EGR, returning to the intake side of the cylinder on the basis of an updated stable combustion limitation mass. an EGR control unit configured to control an EGR flow rate of the EGR mechanism; and a humidity detection unit configured to directly or indirectly detect humidity of an ambient air supplied to the cylinder, wherein the EGR control unit is configured to compute a moisture amount of the ambient air, M H2O,air, and a moisture amount of the recirculating exhaust gas, β, and is configured to control the EGR mechanism on the basis of a stable combustion limitation cylinder mass, M max,map, set depending on a combustion state of the cylinder, a mass of the air, m air, introduced into the cylinder, and a mass of fuel, M Fuel, and the moisture amount finally introduced into the cylinder, wherein the internal combustion engine further has a supercharger and a catalyst placed in a downstream side of a turbine of the supercharger, the EGR mechanism has a high-pressure EGR mechanism configured to return the exhaust gas from an outlet port in an upstream side of the turbine of the supercharger to an inlet port in a downstream side of the compressor of the supercharger and a low-pressure EGR mechanism configured to return the exhaust gas from the outlet port in a downstream side of the catalyst to the inlet port in an upstream side of the compressor of the supercharger, and the EGR control unit is configured to set the stable combustion limitation cylinder mass, M max,map, to be large when the exhaust gas is returned to the intake side of the cylinder using the high-pressure EGR mechanism, compared to a case where the exhaust gas is recirculated using the low-pressure EGR mechanism and is configured to control the exhaust gas amount, M EGR, returning to the intake side of the cylinder on the basis of an updated stable combustion limitation mass.