The present invention provides techniques to calculate the number of surviving and the number of deaths while still concealing survival time data. The present invention includes: a group data position calculation means configured to calculate a share [[gA]] of a sequence gA and a share [[gB]] of a sequence gB represented by predetermined equations from a share [[g]] of a sequence g of values of group of survival time data included in a survival time data set D; a group data number calculation means configured to calculate a share [[sA]] and a share [[sB]] from a share [[t]] of a sequence t of values of time of survival time data included in the survival time data set D, the share [[gA]], and the share [[gB]], by [[sA]]=GroupSum ([[gA]], [[t]]), [[sB]]=GroupSum ([[gB]], [[t]]); and a survival number calculation means.