A method for obtaining road traffic information using billing information, comprising the steps of: setting a reference value of a road traffic state according to a number of generated telephone calls associated with a base station installed on a highway tollgate and having one sector dedicatedly assigned for the highway, and wherein the telephone calls are generated by a mobile terminal while a car in which a user holding the mobile terminal rides enters the highway follgate, and wherein the mobile terminal generating the telephone call sends billing informaton; extracting on a date-by-date basis and a time zone-by-zone basis the number of attempted telephone calls associated with the base station installed on the highway tollgate at predetermined time intervals; comparing the extracted number of attempted telephone calls with the set reference value; and determining in accordance with the results of the comparison a road traffic state; wherein the road traffic state is a smooth road traffic state when the number of attempted telephone calls associated with the base station on the highway tollgate is less than 20% higher than the reference value, wherein the road traffic state is a delay road traffic state when the number of attempted telephone calls associated with the base station on the highway tollgate is 20% to 50% higher than the reference value, wherein the road traffic is a congestion road traffic state when the number of attempted telephone calls associated with the base station on the highway tollgate is 50% to 70% higher than the reference value, and wherein the road traffic state is a serious road traffic congestion state when the number of attempted telephone calls associated with the base station on the highway tollgate is 100% higher than the reference value. setting a reference value of a road traffic state according to a number of generated telephone calls associated with a base station installed on a highway tollgate and having one sector dedicatedly assigned for the highway, and wherein the telephone calls are generated by a mobile terminal while a car in which a user holding the mobile terminal rides enters the highway follgate, and wherein the mobile terminal generating the telephone call sends billing informaton; extracting on a date-by-date basis and a time zone-by-zone basis the number of attempted telephone calls associated with the base station installed on the highway tollgate at predetermined time intervals; comparing the extracted number of attempted telephone calls with the set reference value; and determining in accordance with the results of the comparison a road traffic state; wherein the road traffic state is a smooth road traffic state when the number of attempted telephone calls associated with the base station on the highway tollgate is less than 20% higher than the reference value, wherein the road traffic state is a delay road traffic state when the number of attempted telephone calls associated with the base station on the highway tollgate is 20% to 50% higher than the reference value, wherein the road traffic is a congestion road traffic state when the number of attempted telephone calls associated with the base station on the highway tollgate is 50% to 70% higher than the reference value, and wherein the road traffic state is a serious road traffic congestion state when the number of attempted telephone calls associated with the base station on the highway tollgate is 100% higher than the reference value.