A novel metallic oxide of a Ln-Ca-Sr-Ba-Cu-B-O type and a process for manufacturing such a metallic oxide. The above metallic oxide has a composition expressed by the following formula (I):



        (Ln 1-a Ca a )(Sr 2-b Ba b )(Cu 3-c B c )O d    (I)



wherein Ln is one or more kinds of elements selected from the group consisting of Y and lanthanoid elements except for Ce and Tb and wherein the following conditions are met: 0.1≦a≦0.5, 0.7≦b≦1.7, 0.1≦c≦0.5, and 6.5≦d≦7.5. A process for manufacturing the metallic oxide has the following steps. A mixture of materials including H₃BO₃ used as a starting material of B is prepared. The resultant mixture is heated at a rate of 5°C or lower per minute up to 900°C or lower. Then, it is heated in an oxygen atmosphere at a range from 900 - 1050°C.