A child lock mechanism, comprising: a base member adapted to be assembled to a door of a vehicle; a first lever rotatably assembled to the base member and adapted to be linked with a latch mechanism; a second lever rotatably assembled to the base member and adapted to interlock with an inside door handle; and an intermediate member arranged between the first lever and the second lever in a state in which the intermediate member is assembled to the first lever and is not assembled to the second lever, the intermediate member being allowed to be retained at an unset position or a set position, the child lock mechanism being structured in such a manner that, in a state in which the intermediate member is retained at the unset position, a movement of the second lever is transmittable to the first lever through the intermediation of the intermediate member, and in a state in which the intermediate member is retained at the set position, the movement of the second lever fails to strike the intermediate member and thus is untransmittable to the first lever, wherein, in the state in which the intermediate member is retained at the unset position, the intermediate member is rotatable relative to the base member, and a rotation center of the first lever relative to the base member and a rotation center of the intermediate member relative to the base member are arranged coaxially with each other, characterized in that the rotation center of the first lever relative to the base member is set at a position different from a rotation center of the second lever relative to the base member, and in that a rotation locus, along which a region of the intermediate member engageable with the second lever is rotated relative to the base member when the intermediate member is retained at the unset position, and a rotation locus, along which a region of the second lever engageable with the intermediate member is rotated relative to the base member, are set to be tangent to each other on a line connecting the rotation center of the first lever and the rotation center of the second lever. a base member adapted to be assembled to a door of a vehicle; a first lever rotatably assembled to the base member and adapted to be linked with a latch mechanism; a second lever rotatably assembled to the base member and adapted to interlock with an inside door handle; and an intermediate member arranged between the first lever and the second lever in a state in which the intermediate member is assembled to the first lever and is not assembled to the second lever, the intermediate member being allowed to be retained at an unset position or a set position, the child lock mechanism being structured in such a manner that, in a state in which the intermediate member is retained at the unset position, a movement of the second lever is transmittable to the first lever through the intermediation of the intermediate member, and in a state in which the intermediate member is retained at the set position, the movement of the second lever fails to strike the intermediate member and thus is untransmittable to the first lever, wherein, in the state in which the intermediate member is retained at the unset position, the intermediate member is rotatable relative to the base member, and a rotation center of the first lever relative to the base member and a rotation center of the intermediate member relative to the base member are arranged coaxially with each other, characterized in that the rotation center of the first lever relative to the base member is set at a position different from a rotation center of the second lever relative to the base member, and in that a rotation locus, along which a region of the intermediate member engageable with the second lever is rotated relative to the base member when the intermediate member is retained at the unset position, and a rotation locus, along which a region of the second lever engageable with the intermediate member is rotated relative to the base member, are set to be tangent to each other on a line connecting the rotation center of the first lever and the rotation center of the second lever.