Field load tests were carried out to evaluate the dynamic properties of Ssanggae Bridge as an existing reinforced concrete bridge. The field load tests consisted of vehicle load tests, resonance tests using an exciter and proof load tests by a hydraulic loading system. In this paper, dynamic properties were evaluated based on the field test results measured from resonance condition and vehicle-induced vibration. Moreover, the mass effect of vehicle loading was investigated depending on its position and speed, and the dynamic serviceability related to human response to vibration was surveyed according to the comfort limit considering time duration of vibration.