In this study, a shock absorber whose orifice area changes according to the oil pressure inside the absorber is developed. The orifice widens and narrows when the oil pressure is high and low, respectively; thus, the orifice area changes according to the oil pressure, in other words, according to the extension/compression velocity. It is well known that the damping force can be expressed as $C{cdot}v^{alpha}$. For fluid film damping, the force is proportional to velocity, i.e., ${alpha}=1$, and for orifice damping, it is proportional to the square of velocity, i.e., ${alpha}=2$. The shock absorber proposed in this paper can exhibit different relationships between the damping force and velocity because the orifice area changes according to the induced oil pressure. The motivation of this study is to develop a method for designing a shock absorber with desired values of C and ${alpha}$ which is not just 1 or 2. Theoretical and experimental studies have been conducted to verify the damping characteristics of the shock absorber. The effect of some major design parameters on damping characteristics has been also examined to relate the design parameters to the damping characteristics.