AbstractHemicellulose and lignin, which are main components of wood biomass with different structures, were carbonized and activated by KOH to prepare wood biomass‐derived porous carbons (WBM‐PCs). The resulting WBM‐PCs were characterized by SEM, XRD, Raman, FI‐IR, and N2‐adsorption/desorption isotherms, and successfully utilized as an effective modifier on the glassy carbon electrode surface (GCE) for simultaneous electrochemical determination of dihydroxybenzene isomers, i. e. hydroquinone (HQ) and catechol (CC), which are highly toxic and non‐degradable. The resulting WBM‐PCs‐modified GCEs allowed simultaneous determination of HQ and CC with cyclic voltammetry and constant‐potential amperometry. The linear range for determination of HQ by hemicellulose‐derived carbon (HC) was from 1.0 to 3000 μmol/L with the limit of detection (LOD) of 1.05 μmol/L, and that for CC was from 1.0 to 5000 μmol/L with LOD of 0.4 μmol/L. For lignin‐derived carbon (LC), the linear range for HQ was from 0.5 to 1000 μmol/L with LOD of 0.095 μmol/L, and that for CC was from 0.5 to 3000 μmol/L with LOD of 0.15 μmol/L. These results imply that wood biomass (hemicellulose and lignin), which is sustainable, renewable and environment‐friendly material, have potential as an effective precursor of electrochemically active porous carbon materials applicable to various electrochemical sensors.