A base station in a spread communication system having a particular channel for establishing synchronization, comprising: at least one transmitting means for varying a transmission power of a spread signal on the particular channel of each of a plurality of carrier frequencies which include a first carrier frequency and a second carrier frequency, and transmitting each spread signal over each of the plurality of carrier frequencies; measuring means for measuring the number of mobile stations accommodated in the base station, or a transmission quality of a reception signal from the mobile station; and controlling means for controlling the number of mobile stations accommodated in the first carrier frequency and the number of mobile stations accommodated in the second carrier frequency, wherein when the number of mobile stations accommodated in the first carrier frequency is large while the number of mobile stations accommodated in the second carrier frequency is small, or when the transmission quality measured on the first carrier frequency is low while the transmission quality measured on the second carrier frequency is high, the controlling means decreases the number of mobile stations to be accommodated in the first carrier frequency by decreasing the transmission power of the spread signal transmitted on the particular channel of the first carrier frequency, and increases the number of mobile stations to be accommodated in the second carrier frequency by increasing the transmission power of the spread signal transmitted on the particular channel of the second carrier frequency, the spread signal includes a first portion and a second portion, the first portion is not spread with a long spread code unique to the particular channel of the base station but is spread with a short spread code common to all of base stations, the second portion is spread with both the long spread code and the short spread code, and when decreasing the transmission power of the spread signal transmitted on the particular channel of the first carrier frequency, the controlling means decreases the transmission power for transmitting the first portion and controls the transmitting means to transmit the second portion with the transmission power unchanged. at least one transmitting means for varying a transmission power of a spread signal on the particular channel of each of a plurality of carrier frequencies which include a first carrier frequency and a second carrier frequency, and transmitting each spread signal over each of the plurality of carrier frequencies; measuring means for measuring the number of mobile stations accommodated in the base station, or a transmission quality of a reception signal from the mobile station; and controlling means for controlling the number of mobile stations accommodated in the first carrier frequency and the number of mobile stations accommodated in the second carrier frequency, wherein when the number of mobile stations accommodated in the first carrier frequency is large while the number of mobile stations accommodated in the second carrier frequency is small, or when the transmission quality measured on the first carrier frequency is low while the transmission quality measured on the second carrier frequency is high, the controlling means decreases the number of mobile stations to be accommodated in the first carrier frequency by decreasing the transmission power of the spread signal transmitted on the particular channel of the first carrier frequency, and increases the number of mobile stations to be accommodated in the second carrier frequency by increasing the transmission power of the spread signal transmitted on the particular channel of the second carrier frequency, the spread signal includes a first portion and a second portion, the first portion is not spread with a long spread code unique to the particular channel of the base station but is spread with a short spread code common to all of base stations, the second portion is spread with both the long spread code and the short spread code, and when decreasing the transmission power of the spread signal transmitted on the particular channel of the first carrier frequency, the controlling means decreases the transmission power for transmitting the first portion and controls the transmitting means to transmit the second portion with the transmission power unchanged.