A lubricator comprising: an air bleeder configured to remove air out of a lubricant supply conduit , the air bleeder comprising: the lubricant supply conduit through which a lubricant is supplied to a mixing valve located in a machine tool; a lubricant tank in which the lubricant is stored; a branching portion located along the lubricant supply conduit ; a return conduit connecting the branching portion and the lubricant tank to each other, wherein the lubricant supply conduit comprises a first supply conduit connecting the lubricant tank and the branching portion to each other, and a second supply conduit connecting the branching portion and the mixing valve to each other, and wherein at the branching portion , an upper-stream end of the return conduit is located above an upper-stream end of the second supply conduit ; the mixing valve being configured to mix the lubricant and air together; an air supply conduit through which the air is supplied to the mixing valve ; and a fluid mixture supply conduit which is located between the mixing valve and a lubrication target portion of the machine tool and through which a fluid mixture of the lubricant and the air is supplied to the lubrication target portion , wherein the second supply conduit , which connects the branching portion and the mixing valve to each other, has a length greater than a length of the first supply conduit , which connects the lubricant tank and the branching portion to each other. an air bleeder configured to remove air out of a lubricant supply conduit , the air bleeder comprising: the lubricant supply conduit through which a lubricant is supplied to a mixing valve located in a machine tool; a lubricant tank in which the lubricant is stored; a branching portion located along the lubricant supply conduit ; a return conduit connecting the branching portion and the lubricant tank to each other, the lubricant supply conduit through which a lubricant is supplied to a mixing valve located in a machine tool; a lubricant tank in which the lubricant is stored; a branching portion located along the lubricant supply conduit ; a return conduit connecting the branching portion and the lubricant tank to each other, wherein the lubricant supply conduit comprises a first supply conduit connecting the lubricant tank and the branching portion to each other, and a second supply conduit connecting the branching portion and the mixing valve to each other, and a first supply conduit connecting the lubricant tank and the branching portion to each other, and a second supply conduit connecting the branching portion and the mixing valve to each other, and wherein at the branching portion , an upper-stream end of the return conduit is located above an upper-stream end of the second supply conduit ; the mixing valve being configured to mix the lubricant and air together; an air supply conduit through which the air is supplied to the mixing valve ; and a fluid mixture supply conduit which is located between the mixing valve and a lubrication target portion of the machine tool and through which a fluid mixture of the lubricant and the air is supplied to the lubrication target portion , wherein the second supply conduit , which connects the branching portion and the mixing valve to each other, has a length greater than a length of the first supply conduit , which connects the lubricant tank and the branching portion to each other. <EOS>