1. A method of interpretation service for voice on the phone wherein an interpretation server displays a translation database stored in said interpretation server on a screen of a mobile terminal connected via a mobile Internet access network, switches connection with said mobile terminal to connection with a telephone network upon reception of an instruction to connect to a language interpretation service from said mobile terminal, receives user voice input from the mobile terminal via the telephone network, recognizes said user voice, interprets said recognized user voice into an expression in different language, and outputs voice corresponding to said interpreted expression in different language to said mobile terminal via the telephone network, and wherein said interpretation server displays questionnaire entries for user registration stored in said interpretation server on a screen of a terminal connected via an Internet access network, creates and stores a user profile based on an answer for said questionnaire entries for user registration from said terminal, customizes and stores a translation database based on said user profile, and provides a interpretation service by referencing said customized translation database.