A steering device for a vehicle includes a planet gear mechanism which can vary transmission ratio, and a lock mechanism for fixing the transmission ratio. The planet gear mechanism includes a first sun gear connected to a steering member, a second sun gear connected to turning wheels, a planet gear which is meshed with both the first and second sun gears and a carrier in an annular shape which supports the planet gear. The lock mechanism includes a restraining member which is engageable with the carrier thereby to restrain rotation of the carrier.