Colour of wood changes both during natural aging and during heat treatment. Colour measuring, which is non-destructive and requires only a small area, might be an useful tool as an aging or deterioration index. Exact modelling of colour changes is important not only to predict deterioration but also to understand the aging and deterioration mechanism of wood. This study deals with the modelling of colour changes that occur both during natural aging and during heat treatment by using kinetic analysis. For better understanding of the process of colour change, we employed multi-process kinetic analysis.