To provide a crystal oscillator capable of making excellent electromagnetic shield performance by forming a whole packet of metal, and easily realizing surface mounting and thinning.

An electrode terminal 4 is sealed so as to be insulated through a sealing glass 3 in a through-hole 2 formed in a metallic base 1 made of thin plate materials. The sealing glass 3 is extended from the inside of the through- hole 2 to the periphery of the through hole 2 on the upper and lower faces of the metallic base 1. A printed circuit board 11 on which an IC chip 12 and a crystal piece 14 are mounted is adhered to the upper face of the metallic base 1. A metallic cap 7 is welded to the upper face of the metallic base 1, and the printed circuit board 11 is housed in an air-tight space 8.