A dial device having a rotation preventing function, the dial device comprising: a fixed member; a rotatable rotary member that is rotatable around a rotation axis with respect to the fixed member according to rotating operation by an operator; a double knock mechanism including a pressed member (6, 30a) movable to a first position and a second position on the rotation axis according to pressing operation by the operator, a follower that performs rotation around the rotation axis and movement in an axial direction according to the movement of the pressed member (6, 30a) to the first position and the second position, and a control member that rotates the follower and controls movement of the follower in the axial direction corresponding to the first position and the second position of the pressed member (6, 30a) in order to alternately hold the pressed member (6, 30a) in the first position and the second position every time the pressed member (6, 30a) is pressed; a moving and engaging member that is rotatable together with the rotation of the rotary member and, when the pressed member (6, 30a) is pressed, the moving and engaging member is pressed via a follower of the double knock mechanism to be movable in the axial direction relatively to the rotary member according to the axial direction position of the follower; a fixed side engaging section that is provided in the fixed member and becomes disengaged with the moving and engaging member and allows the rotation of the rotary member when the pressed member (6, 30a) is present in the first position and becomes engaged with the moving and engaging member and prohibits the rotation of the rotary member when the pressed member is present in the second position; and an elastic member that urges the moving and engaging member in a direction from the second position to the first position of the pressed member (6, 30a) and urges the pressed member (6, 30a) in a direction from the second position to the first position via the moving and engaging member and the follower. a fixed member; a rotatable rotary member that is rotatable around a rotation axis with respect to the fixed member according to rotating operation by an operator; a double knock mechanism including a pressed member (6, 30a) movable to a first position and a second position on the rotation axis according to pressing operation by the operator, a follower that performs rotation around the rotation axis and movement in an axial direction according to the movement of the pressed member (6, 30a) to the first position and the second position, and a control member that rotates the follower and controls movement of the follower in the axial direction corresponding to the first position and the second position of the pressed member (6, 30a) in order to alternately hold the pressed member (6, 30a) in the first position and the second position every time the pressed member (6, 30a) is pressed; a moving and engaging member that is rotatable together with the rotation of the rotary member and, when the pressed member (6, 30a) is pressed, the moving and engaging member is pressed via a follower of the double knock mechanism to be movable in the axial direction relatively to the rotary member according to the axial direction position of the follower; a moving and engaging member that is rotatable together with the rotation of the rotary member and, when the pressed member (6, 30a) is pressed, the moving and engaging member is pressed via a follower of the double knock mechanism to be movable in the axial direction relatively to the rotary member according to the axial direction position of the follower; a fixed side engaging section that is provided in the fixed member and becomes disengaged with the moving and engaging member and allows the rotation of the rotary member when the pressed member (6, 30a) is present in the first position and becomes engaged with the moving and engaging member and prohibits the rotation of the rotary member when the pressed member is present in the second position; and an elastic member that urges the moving and engaging member in a direction from the second position to the first position of the pressed member (6, 30a) and urges the pressed member (6, 30a) in a direction from the second position to the first position via the moving and engaging member and the follower.