Adhesive for heat press molding, wooden board, and manufacturing methods thereof

A manufacturing method of an adhesive for heat press molding, comprising:

• a first step of obtaining a mixture by mixing a poly carboxylic acid and a saccharide;
• a second step of obtaining a reaction product by heat treatment on the mixture;
• a third step of adding at least one of ammonium sulfate and ammonium chloride to the reaction product;
• a fourth step of adding water;
• and
• a fifth step of adding wood powder and evaporating water, wherein
• the first step and the second step are carried out in this order,
• the third step is carried out after the second step,
• the fourth step is carried out after the second step, and
• the fifth step is carried out after the third step or the fourth step.