To make value-added products from small-diameter larch logs it is necessary to reduce the color variation between boards. The effect of heat treatment on the color variation was investigated. Four hundred air-dried larch squares were visually classified into six groups. The largest color difference index between them was 8.8. When they were kiln-dried lower than $120^{circ}C$, their average color difference indexes decreased to less than 6.0 compared with the air-dried. However statistical analyses revealed that kiln-drying largely increased the variation of the indexes of the color elements. Heat-treatment above $150^{circ}C$ increased the color difference indexes with the increase of temperature. The variation of color difference indexes within a group at $190^{circ}C$ were less than the groups at $150^{circ}C$ and $170^{circ}C$. It implies that heat treatment at $190^{circ}C$ could make the color of larch squares uniform.