A seat stand includes a seat support section including an installation plate portion having an upper surface on which a seat is provided and an left control box support section extending from a seat support section to the left side of the seat and supporting a left control box. The left control box support section includes an extension portion extending sideward from the installation plate portion and including an upper surface on which the left control box is supported. A arranging space is provided under the extension portion in such a manner that a connection line extending from the left control box supported on the extension portion is arranged through the arranging space. A cutout portion, formed in the extension portion, penetrates the extension portion in a vertical direction and is open sideward.