To provide large-capacity transformers with a lower-loss and compact core, we devised a hybrid configuration consisting of amorphous wound- and silicon steel stacked-cores. In this study, we manufactured a small model of three-phase five-legged hybrid-core designed with conventional method and evaluated the distribution of magnetic flux density (B). It was proved that the measured B-distribution could be reproduced reasonably with the calculated results using the magnetic circuit analysis. However, the hybrid-core has a challenge for capacity enlargement due to different yoke width between amorphous and silicon steel cores resulting in lower static stability. Hence, we proposed a shape of hybrid-core in which the both yoke widths were aligned to half that of the main-leg part. On the basis of magnetic circuit analysis, we demonstrated that the proposed hybrid-core enabled a 10% higher magnetic flux density than configurations with an amorphous core only, and the increase of iron loss against a conventionally designed hybrid-core was suppressed less than 0.8%.