A work vehicle comprising: a travel vehicle body ; a prime mover section that is provided in a front portion of the travel vehicle body ; a hood that covers the prime mover section ; a driver section that is provided rearward of the prime mover section , the driver section having a driver seat ; an engine that is provided inside the hood ; an air cleaner that is provided inside the hood above the engine for processing external air that is to be supplied to the engine ; an intake tube that is coupled to the air cleaner for taking air into the air cleaner ; and a coupling tube that is coupled between the engine and the air cleaner for supplying, to the engine , processed air that is provided by passing external air through the air cleaner , characterized in that the coupling tube includes a third pipe that is coupled to an upper opening of the engine , a second pipe that curves upward and to the right from the third pipe and extends in a right-left direction of the travel vehicle body , and a first pipe that curves from the second pipe toward an exhaust portion provided on one lateral side of the air cleaner for discharging the processed air, and extends toward the air cleaner ; in that the first pipe extends forward and to the right from the exhaust portion , curves forward and to the left, and is coupled to the second pipe ; in that the second pipe of the coupling tube is formed larger in size or diameter than the first pipe and the third pipe of the coupling tube ; and in that the air cleaner has a longitudinally elongated cylindrical shape, with a longitudinal direction extending parallel with the right-left direction of the travel vehicle body . a travel vehicle body ; a prime mover section that is provided in a front portion of the travel vehicle body ; a hood that covers the prime mover section ; a driver section that is provided rearward of the prime mover section , the driver section having a driver seat ; an engine that is provided inside the hood ; an air cleaner that is provided inside the hood above the engine for processing external air that is to be supplied to the engine ; an intake tube that is coupled to the air cleaner for taking air into the air cleaner ; and a coupling tube that is coupled between the engine and the air cleaner for supplying, to the engine , processed air that is provided by passing external air through the air cleaner , characterized in that the coupling tube includes a third pipe that is coupled to an upper opening of the engine , a second pipe that curves upward and to the right from the third pipe and extends in a right-left direction of the travel vehicle body , and a first pipe that curves from the second pipe toward an exhaust portion provided on one lateral side of the air cleaner for discharging the processed air, and extends toward the air cleaner ; in that the first pipe extends forward and to the right from the exhaust portion , curves forward and to the left, and is coupled to the second pipe ; in that the second pipe of the coupling tube is formed larger in size or diameter than the first pipe and the third pipe of the coupling tube ; and in that the air cleaner has a longitudinally elongated cylindrical shape, with a longitudinal direction extending parallel with the right-left direction of the travel vehicle body . <EOS>