A reactor includes a separation membrane permeable to a product of a conversion reaction of a raw material gas containing at least hydrogen and carbon oxide to a liquid fuel, a non-permeation side flow path extending in an approximately vertical direction on a non-permeation side of the separation membrane, the raw material gas flowing through the non-permeation side flow path, and a catalyst configured to fill the non-permeation side flow path and promote the conversion reaction. The catalyst includes a first layer and a second layer disposed upward of the first layer, and a mean equivalent circle diameter of catalyst particles included in the first layer is larger than a mean equivalent circle diameter of catalyst particles included in the second layer.