In the article, a 3-D wideband polarization-rotating surface (PRS) is presented. The proposed until cell is made of a slotline-microstrip-slotline scheme, which is linearly coupled on orthogonal printed circuit boards (PCBs). The microstrip is turned at right angle to couple the two slotline. Under the incidence of linear polarization parallel to the slotline, the incident spatial waves are transformed into guided waves, and then coupled to the microstrip. Subsequently, the incident waves are reconverted into the free space with an orthogonal direction, resulting in wideband 90° polarization rotation. To simplify the design procedure, a transmission-line circuit model is first constructed and synthesized with equal-ripple Chebyshev function. The circuit parameters can be achieved from the specified fractional bandwidth (FBW) and return loss (RL). As an example, a fifth-order with FBW of 110% and RL of 10 dB is designed and simulated, whose physical parameters are accurately extracted from the calculated circuit parameters. Good agreement is observed between the simulated and the theoretical results.