It is an important problem for maintenance and rehabilitation of existing bridges to develop a method of evaluating safety such as remaining life and load carrying capacity of bridges. This paper describes a method of safety evaluation of concrete bridges in service together with verification of the evaluated results based on field tests. The field tests were performed under static loading by test trucks for application to the System Identification Method, and also under dynamic loading by falling mass for application to the Modal Analysis. The safety factors for flexural and shear failures were evaluated from the field tests. These results were verified through the ultimate load test carried out in field on the reinforced concrete main girders isolated by cutting off from the bridge system. Finally, remaining life of the bridge was predicted by application of fuzzy set theory which deal with the subjective information of bridge engineers.