A method for calculating a dangerous spot and time for a computer to execute a process includes, detecting, by at least two mobile bodies, an avoidance action, which is an action that indicates a possibility that each mobile body has avoided a collision with another mobile body, based on locus data of a plurality of mobile bodies that belongs to a predetermined area; calculating an evaluation value that indicates a possibility that an avoidance action by one of the two mobile bodies has occurred under an influence of an avoidance action by another one; and calculating, based on the evaluation value, a collision risk in an area where a plurality of mobile bodies is concentrated.