To provide a mirror stay for a truck having a low-cost structure capable of suppressing occurrence of a whistling sound during travelling while satisfying requisites of a protrusion on the outside of a vehicle in relation to the mirror stay for the truck.

The mirror stay for the truck connected with a bolt and a nut between the vehicle body of the truck and a mirror arm which supports a side mirror is characterized in that the bolt and nut are connected at a joint part formed in a cylindrical shape satisfying the requisites of the protrusion on the outside of the vehicle and the mirror stay for the truck covers the bolt and the nut on the joint part, wherein a notch is disposed on the joint part formed in a cylindrical shape. Further in the mirror stay for the truck, the notch is disposed over the tube bottom part from the opening of the joint part shaped in the cylindrical shape.