A laser oscillator capable of detecting scattered light intensity when a laser beam is incident on an end surface of a fiber more appropriately is provided. A laser oscillator monitoring control system includes: a scattered light detection unit that detects a scattered light intensity on an input end surface of a process fiber of a fiber laser oscillator; a control unit that controls a laser output value on the basis of a laser output command value from a CNC and a detection result obtained by the scattered light detection unit; a normal scattered light calculation unit that calculates a normal index value; a first threshold setting unit that sets a first threshold indicating an abnormality resulting from a contamination and/or a scratch; a second threshold setting unit that sets a second threshold indicating an abnormality resulting from an optical axis shift; and a third threshold setting unit that sets a third threshold indicating an abnormality of a level in which a component is destroyed. The control unit controls a laser output value on the basis of the scattered light intensity detected by the scattered light detection unit, the first threshold, the second threshold, and the third threshold.