In this study, a risk matrix for maintaining the deteriorated RC structures was proposed, in which the difference between the results based on investigation and the actual performance was regarded as risk. The risk matrix was defined as the relation between the degree of material deterioration and the level of influence on the structural performance. This matrix was characterized by involving the range of risk reduction that serves as an index for determining the need for repair. In addition, survey results from an actual RC structure that had undergone the combined damage of frost and salt for more than forty years in Hokkaido were applied to the proposed risk matrix.