A joint mechanism for a mowing machine which can be easily assembled and disassembled, including a support member of a casing which houses a cylindrical damper, which prevents vibration of a power unit from being transmitted to a rod, a holder in which the rod is inserted, and a clamp, which clamp prevents the damper and the holder from unintentionally separating from the support member, being inserted therein. The clamp has a flexible arm which extends in the direction of an output shaft of a power unit, and an engagement hook is formed on the tip of the arm. An engagement hole which the engagement hook of the clamp engages is provided on the support member.