A conveyance seat device, comprising: a seat being a saddle-type seat on which an occupant of a conveyance sits to straddle; and a seat height adjustment unit which is attached below the seat and is able to adjust a height position of the seat, wherein the seat height adjustment unit includes a rotation link which is configured to rotate together with the seat with respect to a main body of the conveyance to adjust the height position of the seat and a flexible cover member that covers the rotation link from the outside in a front to back direction of the seat and a width direction of the seat, wherein the seat height adjustment unit includes a plate-shaped upper link support member that is provided between the seat and the rotation link and is used so that an upper end portion of the rotation link is attached thereto and a lower link support member that is configured to be provided between the rotation link and the main body of the conveyance and is used so that a lower end portion of the rotation link is attached thereto, wherein the rotation link is covered by the cover member, the upper link support member, and the lower link support member, wherein the seat height adjustment unit is able to move the seat between a normal position and an upper position in which the seat is moved above the normal position, wherein the cover member changes its shape in accordance with a movement operation of the seat and is configured to be folded when the seat moves from the upper position to the normal position, characterized in that the cover member includes a cover overhanging portion which is provided so that a lateral portion corresponding to the rotation link in the cover member projects outward when the cover member is folded. a seat being a saddle-type seat on which an occupant of a conveyance sits to straddle; and a seat height adjustment unit which is attached below the seat and is able to adjust a height position of the seat, wherein the seat height adjustment unit includes a rotation link which is configured to rotate together with the seat with respect to a main body of the conveyance to adjust the height position of the seat and a flexible cover member that covers the rotation link from the outside in a front to back direction of the seat and a width direction of the seat, wherein the seat height adjustment unit includes a plate-shaped upper link support member that is provided between the seat and the rotation link and is used so that an upper end portion of the rotation link is attached thereto and a lower link support member that is configured to be provided between the rotation link and the main body of the conveyance and is used so that a lower end portion of the rotation link is attached thereto, wherein the rotation link is covered by the cover member, the upper link support member, and the lower link support member, wherein the seat height adjustment unit is able to move the seat between a normal position and an upper position in which the seat is moved above the normal position, wherein the cover member changes its shape in accordance with a movement operation of the seat and is configured to be folded when the seat moves from the upper position to the normal position, characterized in that the cover member includes a cover overhanging portion which is provided so that a lateral portion corresponding to the rotation link in the cover member projects outward when the cover member is folded.