A mobile terminal used in a code division multiple access mobile communication system in which a base station transmits a control signal via perch channels (106, 107) formed such that a long period code assigned to said base station and a first short period code are mapped in a first section of a first perch channel and a second short period code is mapped in a long period code masked second section of the first perch channel and a third short period code is mapped in a long period code masked second section of said second perch channel, the second short period code being a short code common to base stations of the mobile communication system and the third short code being a group identification short code for identifying a group of long codes of which the long period code is a member, said mobile terminal comprising: an RF unit for converting a received signal of a carrier frequency received from an antenna to a baseband signal; a correlator for receiving input of said baseband signal and calculating a correlation value for said baseband signal by using said second short period code to establish slot timing synchronization; and a group identification short code detection unit for receiving input of said baseband signal, storing the long code masked section of said base band signal and calculating correlation values for said stored long code masked section and a candidate third short period code to identify the third short period code used by the base station based on the highest one of the correlation values, and a long code detection unit for detecting the long code based on the identified third short period code, characterized in that said second and third short period codes have a spreading factor shorter than a spreading factor of said first short period code, and said second section is time-divided into a plurality of sub-sections, said second short period code being mapped in a first sub-section and said third short period code being mapped in a second sub-section wherein the first and second sub-sections may be any of the plurality of sub-sections, and in that a sub-section of the long code masked section in which the third short code is detected is used to determine the group of long codes. an RF unit for converting a received signal of a carrier frequency received from an antenna to a baseband signal; a correlator for receiving input of said baseband signal and calculating a correlation value for said baseband signal by using said second short period code to establish slot timing synchronization; and a group identification short code detection unit for receiving input of said baseband signal, storing the long code masked section of said base band signal and calculating correlation values for said stored long code masked section and a candidate third short period code to identify the third short period code used by the base station based on the highest one of the correlation values, and a long code detection unit for detecting the long code based on the identified third short period code, characterized in that said second and third short period codes have a spreading factor shorter than a spreading factor of said first short period code, and said second section is time-divided into a plurality of sub-sections, said second short period code being mapped in a first sub-section and said third short period code being mapped in a second sub-section wherein the first and second sub-sections may be any of the plurality of sub-sections, and in that a sub-section of the long code masked section in which the third short code is detected is used to determine the group of long codes.