An obstacle detection system for a work vehicle comprising: a plurality of imaging devices (81, 82, 83, 84), each of which is configured to capture an image of surroundings of the work vehicle; and an image processing device that is configured to perform obstacle discrimination processing for discriminating an obstacle on the basis of the images from the plurality of imaging devices by a time division system, characterized in that the plurality of imaging devices (81, 82, 83, 84) and the image processing device are configured to generate an all-around image of the work vehicle and in that the image processing device is configured to change a processing target cycle per unit time for each of the imaging devices (81, 82, 83, 84) in the time division system according to a travel direction and a vehicle speed of the work vehicle, wherein the image processing device is configured to: hasten a processing target cycle per unit time for each of the imaging devices (81, 82, 83, 84) having a travel direction of the work vehicle as the imaging range, and slow a processing target cycle per unit time for each of the imaging devices (81, 82, 83, 84) not having a travel direction of the work vehicle as the imaging range, as well as the image processing device is configured to, as speed of the work vehicle increases, hasten a processing target cycle per unit time for each of the imaging devices (81, 82, 83, 84) having a travel direction of the work vehicle as the imaging range, and slow a processing target cycle per unit time for each of the imaging devices (81, 82, 83, 84) not having a travel direction of the work vehicle as the imaging range. a plurality of imaging devices (81, 82, 83, 84), each of which is configured to capture an image of surroundings of the work vehicle; and an image processing device that is configured to perform obstacle discrimination processing for discriminating an obstacle on the basis of the images from the plurality of imaging devices by a time division system, characterized in that the plurality of imaging devices (81, 82, 83, 84) and the image processing device are configured to generate an all-around image of the work vehicle and in that the image processing device is configured to change a processing target cycle per unit time for each of the imaging devices (81, 82, 83, 84) in the time division system according to a travel direction and a vehicle speed of the work vehicle, wherein the image processing device is configured to: hasten a processing target cycle per unit time for each of the imaging devices (81, 82, 83, 84) having a travel direction of the work vehicle as the imaging range, and slow a processing target cycle per unit time for each of the imaging devices (81, 82, 83, 84) not having a travel direction of the work vehicle as the imaging range, as well as the image processing device is configured to, as speed of the work vehicle increases, hasten a processing target cycle per unit time for each of the imaging devices (81, 82, 83, 84) having a travel direction of the work vehicle as the imaging range, and slow a processing target cycle per unit time for each of the imaging devices (81, 82, 83, 84) not having a travel direction of the work vehicle as the imaging range. hasten a processing target cycle per unit time for each of the imaging devices (81, 82, 83, 84) having a travel direction of the work vehicle as the imaging range, and slow a processing target cycle per unit time for each of the imaging devices (81, 82, 83, 84) not having a travel direction of the work vehicle as the imaging range, as well as the image processing device is configured to, as speed of the work vehicle increases, hasten a processing target cycle per unit time for each of the imaging devices (81, 82, 83, 84) having a travel direction of the work vehicle as the imaging range, and slow a processing target cycle per unit time for each of the imaging devices (81, 82, 83, 84) not having a travel direction of the work vehicle as the imaging range.