Cryptomeria japonica was treated with pyridinium chloride ([Py]Cl)-water mixtures under various conditions to determine the optimum conditions for efficient production of furan compounds, such as 2-hydroxyacetylfuran (2-HAF), 5-hydroxymethylfurfural (5-HMF), and furfural. The maximum total yield of furan compounds, i.e., 9.24 wt.%, was obtained by the treatment of C. japonica with a 90% [Py]Cl and 10% water (w/w) solution for 30 min at 120 °C with a sample loading of 6 wt.%. The highest yield of 2-HAF from C. japonica was obtained by treatment for 3 min at 160 °C without the addition of water, although the total yield of furan compounds was lower than that obtained under the optimum treatment conditions. Scale-up of this process for efficient production of furan compounds from C. japonica was successfully performed under the optimum treatment conditions. In addition, the yields of 2-HAF and 5-HMF increased when ball-milled C. japonica containing low-crystallinity cellulose was treated under the optimum conditions.