PURPOSE: To make a titled optical radiator suitable for a plant cultivation by utilizing plural rotatable transparent plates, and emitting effectively from a cable a solar light or an artificial light which has been propagated through the inside of a photoconductor cable.

CONSTITUTION: While a plant is small, when upper transparent plates 131W 136 are made vertical, and a lower transparent plate 137 is inclined diagonally, a light led into a cylindrical body 11 is reflected by the transparent plate 137, emitted to the outsid of the cylindrical body 11 and irradiated to the plant. As the plant grows larger, when the upper passive reflector is inclined, a light can always be supplied from the upper part of the plant, and a part of light which has passed through the inclined transparent plate part is supplied to the lower part, and emitted to the inside. In this way, a light of a large quantity is supplied to the upper part of the plant, a light of a small quantity is supplied to the lower part, and accordingly, the plant can be reared most efficiently.