An oil supply device for a conveyance device, comprising a conveyance chain, an upper rail in which the chain travels and an oil supply device provided above the upper rail. A groove portion is provided at an inner surface side of the upper rail. An upper key member is positioned between the groove portion and the chain to support the upper portion of the chain. An oil supply hole, through which oil passes, is formed at a position of the upper rail which corresponds to a position above the upper key member. The oil, dropped from the oil supply device, passes through the oil supply hole of the upper rail and is applied to an upper surface of the upper key member. The oil applied to the upper surface of the upper key member is flown along the upper surface and the side surface thereof and supplied to the chain.