To provide a surface-mounting oscillator capable of preventing its terminals from being stained with a protective resin and increasing its productivity.

In a surface-mounting crystal oscillator equipped with a crystal piece 2 placed and hermetically sealed in a recessed portion of one main surface of a container 1 which is rectangular when plan-viewed and an IC chip 3 having IC terminals in a recessed portion of the other main surface of the container 1 with its circuit functional surface fixed to the recessed portion, wherein the recessed portion of the other main surface is filled with a resin 9 for protecting the circuit functional surface of the IC chip 3, notched portions 11 in the thickness direction are formed on the open end surface of each of the four sides constituting the recessed portion of the other main surface of the container 1.