A method for controlling transmission power of a physical random access channel in a mobile communication terminal. The mobile communication terminal sets initial transmission power according to received signal code power when a preamble of the physical random access channel is transmitted to a mobile communication network. A wireless channel environment is identified on the basis of a value of the received signal code power when the preamble must be retransmitted. According to the identified wireless channel environment, transmission power used in a previous preamble is variably increased and retransmission power is set.