This study proposes an accurate mechanical model of a wooden frame with knee-brace type oil dampers. The oil damper used in this study has two remarkable mechanical properties; the one is that the damper works only when subject to compression, and the other is that it is provided with the relief valves to prevent members of framework from being subjected to excessive internal force. In this paper, firstly a dynamic sinusoidal loading test on the damper is conducted to show its dynamic mechanical properties, and it is confirmed that a nonlinear Maxwell model exactly simulates the experimental results. Then, a mechanical model of the wooden frame with knee-brace dampers is constructed taking into consideration a relation between deformation of the damper attached as a knee-brace and story deflection angle. Lastly, a dynamic loading test of the wooden frame installed with dampers is conducted. It indicates that the hysteretic loops and energy calculated by proposed model accurately agree with those obtained by the experiment.