To provide a plasma heating method for molten steel which improves heating ability while preventing the nitriding of the molten steel and prolonging the life of a plasma torch in plasma heating of the molten steel.

In the plasma heating method for heating the molten steel by the plasma arc generated from the plasma torch inserted into a molten steel holding vessel, the torch working gas ejected from the plasma torch is formed of a gaseous mixture composed of gaseous argon and gaseous nitrogen and the flow rate ratio of the gaseous nitrogen is controlled to ≤80%.