There are disclosed a random access method for establishing an individual channel between a radio communication terminal device and a base station device in a short time and a radio communication terminal device executing the random access method. In this device, in step ST320, a RACH sub-channel allocation unit (211) allocates a transmission packet inputted from a replication unit (202) to an arbitrary sub-carrier at the RACH arbitrary time slot at random. In step ST330, an allocation unit (210) judges whether an overlap is generated in the allocation result obtained by the RACH sub-channel allocation unit (211). When the allocation unit (210) judges that an overlap is generated in the allocation result, the allocation unit (210) causes one of the RACH sub-channel allocation units (211) which has caused the overlap to again perform allocation of step ST320. On the other hand, when judgment is made that no overlap is generated in the allocation result, step ST340 is executed.