A parking lock mechanism of the drum-type transmission device comprises a parking gear that is provided on the transmission shaft, a parking operation arm which is selectively operated between a lock position engaging with the parking gear and an unlock position away from the parking gear, a parking release spring for urging the operation arm toward the unlock position, and a parking pushing member which is positioned at a lock position by pushing the operation arm according to the rotation of the drum member from the shift position or the neutral position to the parking position. One end of the transmission operation shaft is located near the operation arm. At one end of the shift operation shaft, there is provided an arm restraining portion that can urge the operation arm toward the unlock position when the drum member is moved from the parking position to the shift position or the neutral position.