To provide a belt fastener and a belt fastening device wherein tension applied to a belt and a sidewall of a platform of a truck is not rapidly canceled even when a belt fastener fixing a load mounted on the platform of the truck is unlocked and generation of a noise due to a violent vibration of the sidewall of the platform of the truck occurring when the fastener is unlocked can be prevented.

A support point 10 between a base 5 and a handle 3 is formed of an elongated hole 8 which is provided on one of the base 5 and the handle 3 and extends in a direction farther away from the base 5 and of a shaft 7 provided on the other. At an end of the handle 3 closer to the base 5, a protrusion 4 which comes over the base 5 and rotates the handle 3 while moving in a direction that the support point 10 comprising the hole 8 and the shaft 7 comes farther away from the base 5 is provided.