The electron transfer between insoluble polymer containing 1‐benzyl‐1,4‐dihydronicotinamide (BNAH) structure (P‐BNAH) and benzoquinone (Q) structure (P‐Q) by use of alloxan (A) as an electron carrier was investigated. Although no reaction occurred on suspending the P‐BNAH and P‐Q in ethanol/water, P‐Q was reduced smoothly to hydroquinone structure (P‐HQ) by addition of A. The results suggest that A was reduced by P‐BNAH to give A radical (A·) or dialuric acid (D) and then A· (or D) reduced P‐Q, whereby A was regenerated and thus indicated that the oxidation reduction between insoluble solid polymers was mediated by A as an electron carrier.