A sheet-medium conveying device comprising: a first sheet-medium stacker part (71, 75) provided on a casing so as to be capable of being opened from and closed to the casing, the first sheet-medium stacker part (71, 75) having a main sheet-medium stacker surface on which a sheet medium is to be placed, the main sheet-medium stacker surface being directed upward when the first sheet-medium stacker part (71, 75) is in an opened state; a second sheet-medium stacker part provided to the first sheet-medium stacker part (71, 75) so as to be capable of being drawn from and inserted into the first sheet-medium stacker part (71, 75), the second sheet-medium stacker part having an expanded sheet-medium stacker surface on which the sheet medium is to be placed, the expanded sheet-medium stacker surface appearing by drawing the second sheet-medium stacker part from the first sheet-medium stacker part (71, 75) when the first sheet-medium stacker part (71, 75) is in the opened state; and an auxiliary member provided on the first sheet-medium stacker part (71, 75) so as to be capable of being moved, the auxiliary member being engaged with the second sheet-medium stacker part so as to be moved together with the drawing of the second sheet-medium stacker part so that the auxiliary member covers a gap portion between the main sheet-medium stacker surface and the expanded sheet-medium stacker surface when the second sheet-medium stacker part is in a drawn state; characterized in that the auxiliary member has a mark indicative of a position of the sheet medium in a direction perpendicular to a conveyance direction of the sheet medium determined according to a size of the sheet medium. a first sheet-medium stacker part (71, 75) provided on a casing so as to be capable of being opened from and closed to the casing, the first sheet-medium stacker part (71, 75) having a main sheet-medium stacker surface on which a sheet medium is to be placed, the main sheet-medium stacker surface being directed upward when the first sheet-medium stacker part (71, 75) is in an opened state; a second sheet-medium stacker part provided to the first sheet-medium stacker part (71, 75) so as to be capable of being drawn from and inserted into the first sheet-medium stacker part (71, 75), the second sheet-medium stacker part having an expanded sheet-medium stacker surface on which the sheet medium is to be placed, the expanded sheet-medium stacker surface appearing by drawing the second sheet-medium stacker part from the first sheet-medium stacker part (71, 75) when the first sheet-medium stacker part (71, 75) is in the opened state; and an auxiliary member provided on the first sheet-medium stacker part (71, 75) so as to be capable of being moved, the auxiliary member being engaged with the second sheet-medium stacker part so as to be moved together with the drawing of the second sheet-medium stacker part so that the auxiliary member covers a gap portion between the main sheet-medium stacker surface and the expanded sheet-medium stacker surface when the second sheet-medium stacker part is in a drawn state; characterized in that the auxiliary member has a mark indicative of a position of the sheet medium in a direction perpendicular to a conveyance direction of the sheet medium determined according to a size of the sheet medium.