We have investigated the characteristics of some layered structural regenerators (multilayer regenerators) with magnetic regenerator materials using a two-stage GM refrigerator. In this study, we newly used Er_0·75Gd_0·25Ni which is expected to be placed in the high-temperature part of the second regenerator. To confirm the effect of Er_0·75Gd_0·25Ni, the heat-exchange efficiency of the regenerator (regenerator efficiency) with Er_0·75Gd_0·25Ni, Er₃Co and Er_0·9Yb_0·1Ni, which were in the volumetric ratio of x: (0.5-x): 0.5 (0≤x≤0.5) was calculated as a function of x by computer simulation. We found that the regenerator efficiency increased when x (i.e. the amount of Er_0·75Gd_0·25Ni) was increased and the optimum value of x was -0.25. We then made two kinds of second regenerators: a triplelayer regenerator with Er_0·75Gd_0·25Ni, Er₃Co and Er_0·9Yb_0·1Ni, which were in the volumetric ratio of 0.25:0.25:0.5, and a doublelayer regenerator with Er₃Co and Er_0·9Yb_0·1Ni, which were in the volumetric ratio of 0.5:0.5. We compared experimentally their refrigeration performances. With the triplelayer regenerator, the lowest temperature was 2.60K at the second stage and the maximum refrigeration capacity at 4.2K was 1.17W. These results were superior to those with the doublelayer regenerator.