Controller for an internal combustion engine with variable valve mechanism

A device for controlling an internal combustion engine based on a temperature of a certain portion in the cylinder, comprising a variable valve mechanism for varying opening areas of at least either the intake valves or the exhaust valves, wherein a temprature of gas in the cylinder is calculated based on the opening area of at least either the intake valve or the exhaust valve varied by the variable valve mechanism, and the internal combustion engine is controlled based on the temperature of gas in the cylinder.