Cucumber plant is widely cultivated in Japan, and its fruit grows rapidly. Automation for cucumber fruit harvesting is more important than for other fruits. In this paper, a cucumber harvesting robot which consisted of a visual sensor, manipulator, hand and traveling device was described. First, the visual sensor should be able to discriminate green fruit from leaves and stems. However, the color of leaves and stems is similar to that of fruit. In addition, the 3-D position of fruit should be detected. Two sensor systems were, therefore, combined for use of the robot: one was a monochrome TV camera with both 550 nm and 850 nm wavelength interference filters to discriminate fruit using spectral reflectance; the other was a photo-electric sensor in which a PSD (position-sensitive device) array was used to measure the distance. Secondly, the robot needs to approach the fruit. The mechanism of the manipulator was investigated based on the morphological properties of cucumber plant so as to adapt a harvesting configuration with high manipulatability and the 6 DOF (degree of freedom) manipulator was manufactured on an experimental basis. Thirdly, the harvesting hand must grip the fruit as well as detect and cut the peduncle. The hand was also constructed experimentally based on the physical properties of cucumber plant. Finally, a harvesting experiment was conducted, after the robotic components were mounted on the traveling device with 4 wheels. The results obtained showed that the use of the robot was suitable for harvesting.