To provide a case for en electronic component, which is low-cost and which is easy to manufacture.

In a process (a), an aluminum alloy disk 1 is arranged directly on the bottom face of a stainless steel case 1 without having an intermediate member interposed. In a process (b), the lower part of the case 1 is placed on an anvil (a support base) 24 in an ultrasonic welding apparatus, an ultrasonic horn (a tool) is brought into contact with the surface of the aluminum alloy disk 2 which is arranged on the bottom face of the case 1, the ultrasonic welding apparatus is operated, and the aluminum alloy disk 2 is bonded to the bottom face of the case 1 through ultrasonic welding. In a process (c), the case 1 is placed on a lower punch 16, the whole surface of the aluminum alloy disk 2 is pressed by an equal force by using an upper formal compression bonding punch 17, and so that the aluminum alloy disk 1 is crushed to make its thickness thin.