To provide a recording layer protecting coating agent which is excellent in giving water resistance to a recording medium, and the recording medium which has a recording layer coated with the agent and has high water resistance.

The recording layer protecting coating agent contains a carboxy group-modified polyvinyl alcohol (A), a polyamide polyamine epihalohydrin (B) and a polyethylene imine (C). The degree of saponification of the carboxy group-modified polyvinyl alcohol (A) is preferably 90-99.5 mol%. The recording medium has the recording layer coated with this coating agent.