To obtain a laser oscillator which has an optical system for confirming a working point or adjusting the optical path and in which the optical axis of guide light does not vary even when a casing is thermally deformed. The laser oscillator includes the casing (10), a pair of optical bases (21, 22) which are connected in parallel to each other by three support bars (24 to 26) extending along the optical axis and respectively support optical components constituting an optical resonator (20), a pair of bellows which connect the optical bases (21, 22) to the casing (10), a coupling member (31) bywhich the optical bases (21, 22) are suspended from the casing (10), a guide-light light source (27) which emits guide light for adjusting an optical component in the optical path from a partially reflecting mirror (23) to a working head and adjusting a working point, and an optical component support member (40) having optical components for guiding laser light. The guide-light light source (27) is arranged on the optical base (22) having the partially reflecting mirror (23).