Embodiments of the present invention may include an internal combustion engine (1) equipped with a blow-by gas circulating means and a control means (40). An intake pipe (31A) is connected to the engine (1), and blow-by gas piping (12) for circulating blow-by gas to the engine (1) is connected to the intake pipe (31A). An internal combustion engine (1) control method includes an environmental condition determination step and a forcible blow-by gas temperature rising step. In the environmental condition determination step, the control means (40) determines whether or not the engine (1) is in an environmental condition in which ice can be generated at a joining portion between the blow-by gas piping (12) and the intake pipe (31A) based at least on a temperature of intake air taken-in through the intake pipe (31A). When it is determined that the engine (1) is in an environmental condition in which ice is generated, the control means (40) changes the operational condition of the engine (1) such that a temperature of the blow-by gas increases in the forcible blow-by gas temperature rising step.