A plant cultivation device and feed-water control method, in which a detected moisture amount to start watering and a water amount to be used per watering are easily determined, includes a plant cultivation container for pooling plant cultivation water; a water-absorbing plant cultivation bed material; a feed-water device for supplying the plant cultivation water to the plant cultivation container; a first moisture sensor for detecting moisture around an immersed part of the plant cultivation bed material; a second moisture sensor for detecting moisture around a growth part of the plant cultivation bed material where a root of a plant is received; and a controller for supplying water when values detected by both of the first and second moisture sensors are below respective reference values, and for stopping water supply when a value detected by either the first or second moisture sensor is above the corresponding reference value.