Disclosed herein is a glue applicator for a corrugator machine in which a starch glue in a glue pan is applied to ridge portions of a corrugated core sheet by an applicator roll, the applicator comprising: a stock tank holding a stock of starch glue; a glue heater having a couple of upper and lower glue pooling chambers for reserving the starch glue supplied from the stock tank, a heat medium chamber defined between the upper and lower pooling chamber and holding a heat medium, a plural number of heat exchange pipes inserted vertically across the heat medium chamber in contact with said heat medium and communicating at the upper and lower ends with the upper and lower pooling chambers to permit flows of the starch glue between the upper and lower pooling chambers, and a steam blow pipe opened into a bottom portion of the heat medium chamber for blowing steam thereinto; and a glue feed pipe connecting the upper pooling chamber of the glue heater to the glue pan.