PURPOSE: To prevent the degradation of water extraction type coffee and lower the acidity by sealing roasted coffee beans and active carbon into a coffee bag body.

CONSTITUTION: Water extraction type coffee bag has a coffee back body filled with roasted coffee bans and active carbon which are mixed preferably at a mixing rate of 3-50wt.% per 100wt.% of the coffee beans on a crude bean basis. Both components act on each other so that the active carbon prevents the degradation of the roasted coffee beans while the active carbon neutralizes pH of a coffee extracted liquid by lowering the acidity thereof. This method allows the use of even the weakly roasted coffee beams or those with intense acidity. In addition, by adsorbing and reducing actions and the like of the active carbon, the bitterness and sharpness of the coffee extraction liquid are intensified while its acidity associated with hourly degradation of the roasted beans, the generation of obnoxious smell, etc., can be suppressed. In actual use, drinking is possible by simply dipping the coffee bag body into water at a normal temperature for 4 hour or more.