Drying of acrylamide (AAm) gels was monitored by using a photon transmission technique. These hydrogels are formed from AAm and N,N'-methylenebis(acrylamide) (Bis) with various water contents by the free-radical crosslinking copolymerization (FCC). The transmitted light intensity, I-tr, increased continuously as AAm gels were dried. The increase in I-tr was attributed to the decrease in the scattered light intensity, I-sc, which might be originated from the contrast between frozen blob clusters and holes in the drying gel. A decrease in I-sc was modeled by using Rayleigh's equation where drying times with various exponents were found to be proportional to the size of the holes. It was observed that the radius of holes, xi (c), decreased in various powers of the drying time depending on water content used during FCC.