1. A computer implemented similarity calculating method, comprising: extracting similarity calculating data, which is determined in advance, by receiving a communication activity record for every user; modeling a communication activity pattern for every user by calculating a value of a static feature from the extracted similarity calculating data; modeling common information between the users by calculating a value of a dynamic feature from the extracted similarity calculating data; calculating a static similarity for each user by using elements of the static feature to which the modeled communication activity pattern is reflected; calculating a dynamic similarity by using the modeled common information for each element of the dynamic feature for every user; and calculating a similarity between the users using the calculated static similarity and the calculated dynamic similarity.