A gas laser apparatus including a laser oscillating section including a blower forcibly circulating a medium gas in a medium circuit, and a blower monitoring section monitoring a maintenance state of the blower. The blower includes a lubricant storage chamber storing a lubricant, and a lubricant monitoring chamber connected to the lubricant storage chamber to ensure fluidic communication therebetween at a position lower than an oil level of a lubricant having a predetermined appropriate volume and stored in the lubricant storage chamber. The blower monitoring section includes a lubricant detecting section detecting that a lubricant stored in the lubricant storage chamber of the blower flows into the lubricant monitoring chamber and at least a part of the lubricant is present in the lubricant monitoring chamber, as a result of internal-pressure change in the lubricant storage chamber, and a lubricant-change judging section monitoring whether the lubricant detecting section detects a presence of the lubricant in the lubricant monitoring chamber, before the laser oscillating section is activated, and judging that, when the lubricant detecting section does not detect the presence, the lubricant stored in the lubricant storage chamber is in a state immediately after a lubricant change.