A piece of apparatus for measuring the peel adhesion behavior of pressure-sensitive adhesive tapes was developed. The apparatus allows peel rates to be varied as any functions of time or peel distance. In a cycle run of the accelerating and decelerating peel processes, nonstationary peeling was investigated over a wide range of peel rates using relatively short-length samples. The resultant behavior in nonstationary peeling indicated that in the interfacial failure regime, a good agreement with the normal stationary peeling can be obtained. This nonstationary peeling apparatus is expected to be useful for evaluation of peel adhesion.