PURPOSE: To prevent damage of ceramic elements and wear of bearing elements and a rotary shaft, by arranging a bearing member for supporting a rotary shaft on an internal peripheral surface of a back metal contained in a bearing casing, and also by arranging an elastic element and a ceramic element in a gap among adjacent back metals and the bearing casing.

CONSTITUTION: A bearing back metal 2 is arranged ringwise on an inside peripheral surface of a bearing casing 1. While a resin bearing 4 for supporting a rotary shaft 3 is arranged inside the bearing back metal 2, a gap is formed among the peripheral ends 2a of the bearing back metals 2 and the bearing casing 1 so as to gradually increase the radial clearance toward the ends 2a. An elastic element 5 is arranged between the gap, and a ceramic element 6 is fixed to the inside surface of the elastic element 5. These elements support the rotary shaft 3 together with the resin bearing 4 by using water as lubricant. Accordingly, it is possible to prevent damage and wear of the resin bearing 4 and the rotary shaft 3, and to improve reliability and safety by compensating the low impact strength of the ceramic element 6 by means of the elastic element 5.