A data communication restriction method for flat rate users is disclosed. The data communication restriction method comprises the steps of: monitoring data communication status of a flat rate user, and determining whether the number of request or communication quantity during a predetermined period exceeded a predetermined threshold (S9); setting the flat rate user as a communication restricted object when it is determined that the threshold was exceeded (S10); and transmitting a communication restriction signal including communication restriction period information to a mobile terminal of the restricted flat rate user, when the restricted flat user requested access again (S11); whereby data communication of the mobile terminal of the restricted flat rate user is restricted during the communication restriction period.