Corrosion of reinforcement concrete structure is a main cause of structural damage that required to repair or replacement. A non-destructive testing (NDT) method to find out the location and degree of corrosion-induced damage is needed. The NDT of ground penetrating radar (GPR) method has been found to be useful to evaluate reinforced concrete structure existences for the continued use or for the repair. This paper presents the study to detect the corrosion using GPR based on image processing technique and artificial neural network (ANN). A method using direct current (DC) power supply with 5% sodium chloride (NaCl) solution is employed for accelerating reinforcement bars (rebars) corrosion before rebars are induced to the reinforced concrete 1 x 1 x 0.3 m mixture. The rebars are corroded in 4 duration of exposure time (0, 1, 3, and 7 days). The 2 GHz of GPR are used for corrosion detection in the reinforced concrete slabs after 28-days of standars moist curing. The GPR data is processed and analyzed by using image processing and ANN, respectively. The result is showed that the corrosion can be detected with 100% of accuracy.