PURPOSE: To roast coffee beans so as to eliminate bitterness in a simple roaster in a short time by half-roasting coffee beans, containing the half-roasted coffee beans in a container unit of an aluminum foil and heating the coffee beans under specific conditions.

CONSTITUTION: Half-roasted coffee beans (d)... are contained in a simple roaster (A) and the container unit (a) is hermetically sealed with a lid unit (b). The coffee beans (d)... are then roasted while rocking the container unit (a) with a strong fire, such as a gas heater. The coffee beans (d)... are burst to product bursting sound. A picking part 14 is subsequently picked to cut off a stopping piece 13 integral with the lid unit (b) and open a ventilating hole and discharge smoke, etc., generated in the interior of the container unit (a) to the outside. Roasting is then carried out while rocking the container unit to provide a desired color.