An outrigger device that is mounted on a vehicle and can switch between a usage state and a storage state, the outrigger device comprising: a lateral outrigger that extends in a vehicle width direction of the vehicle; a vertical outrigger that is extendable and is rotatably coupled to a leading end portion of the lateral outrigger; a first coupling member that constantly couples a first part of the vertical outrigger to the lateral outrigger and serves as a rotational center of the vertical outrigger; a second coupling member that can switch between a first state where a second part of the vertical outrigger is coupled to the lateral outrigger and a second state where the second part is uncoupled from the lateral outrigger; a conversion mechanism that converts a retraction of the vertical outrigger into an upward rotation of the vertical outrigger; and a safety device that prohibits an operation of the conversion mechanism in the first state and permits the operation of the conversion mechanism in the second state, whereby the safety device includes a lock mechanism that can switch between a locked state where the retraction is prohibited and an unlocked state where the retraction is permitted, and the lock mechanism enters into the locked state in the first state, and enters into the unlocked state in the second state, whereby the vertical outrigger includes a first vertical outrigger element and a second vertical outrigger element which are extendably combined, characterised in that the lock mechanism includes a lock member that prohibits the retraction by engaging with the first vertical outrigger element and the second vertical outrigger element in the first state. a lateral outrigger that extends in a vehicle width direction of the vehicle; a vertical outrigger that is extendable and is rotatably coupled to a leading end portion of the lateral outrigger; a first coupling member that constantly couples a first part of the vertical outrigger to the lateral outrigger and serves as a rotational center of the vertical outrigger; a second coupling member that can switch between a first state where a second part of the vertical outrigger is coupled to the lateral outrigger and a second state where the second part is uncoupled from the lateral outrigger; a conversion mechanism that converts a retraction of the vertical outrigger into an upward rotation of the vertical outrigger; and a safety device that prohibits an operation of the conversion mechanism in the first state and permits the operation of the conversion mechanism in the second state, whereby the safety device includes a lock mechanism that can switch between a locked state where the retraction is prohibited and an unlocked state where the retraction is permitted, and the lock mechanism enters into the locked state in the first state, and enters into the unlocked state in the second state, whereby the vertical outrigger includes a first vertical outrigger element and a second vertical outrigger element which are extendably combined, characterised in that the lock mechanism includes a lock member that prohibits the retraction by engaging with the first vertical outrigger element and the second vertical outrigger element in the first state.