To quantize a risk of backing and parallel stages in project management.

A design structure matrix representing the degree of dependency showing dependency among a plurality of tasks included in a project in matrix form is generated first. Then the completion time of each task based upon the start time of the project is computed according to the operation period and precedence relation of the plurality of tasks. The completion time of each task is recorded at a diagonal part of the design structure matrix. Then the backing period from the completion time of a 1st task among the plurality of tasks to the start time of a 2nd task precedent to the 1st task is computed. Lastly, the degree of the dependency of the 1st task on the 2nd task is multiplied by the backing period to computes the degree of backing influence.