We studied chemical kinetics of weathering in the humus horizons of young Andisols from northeastern Japan. Since there is no idealized chronosequence of Andisols, we selected eight pedons that have many similarities in the properties of parent material, soil moisture regime, vegetation, drainage, etc., but show significant differences in soil age and soil temperature. We introduced “soil age normalized to 10°C,” which was defined as the number of years a soil has been subjected to pedogenesis under mean monthly soil temperature (MMST) of 10°C throughout the year. For this calculation, temperature dependency coefficient (Q10) of Al release from volcanic glass was determined to be 1.5 by the laboratory dissolution experiment using separated glass samples. Mean monthly air temperature (MMAT) plus 1°C was employed as MMST based both on the comparison between MMST and MMAT and the determination of diurnal variations of soil temperature. Of the various elements contained in volcanic ash, Al was found to be most reliable for evaluating chemical weathering of the bulk soils, and released Al was determined by the acid oxalate method. The correlation between the soil age normalized to 10°C and acid oxalate extractable Al (Alo) showed that the chemical weathering is expressed as zero-order kinetics.