To provide a low-costing frost prevention device not hurting fruit trees or fruits by processing fuel and pellets made from plants not being fossil fuel, namely vegetation, into granular or columnar pellets with substantially the same size, operating a motor by a controller electrically controlling supply to a pellet combustion part to carry out automation, carrying continuous combustion for a long period of time, and substantially reducing labor of a plantation worker without depending on fossil fuel.

The frost prevention device is a combustion apparatus burning the pellets 1 made from plants. It is characterized by that it has a housing part 2 housing the pellets 1, a carry out means 6 attached to the housing part 2 for carrying out the pellets 1 in the housing part 2 at predetermined amounts, or at a predetermined speed, the motor attached adjacent to the carry out means 6, with an operation interval or an operation speed controlled by the controller 8, and a combustion part 11 receiving and burning the pellets 1 carried in from the carry out means 6 operated by the motor.