A solid medium having a 10 minute-average water absorption rate of at least 0.05 ml/minute, which is obtainable by a method for producing a solid medium comprising the steps of dissolving components of the solid medium other than solvent water into the solvent water, solidifying the obtained solution, and drying the solidified medium to remove water, wherein water is removed in such an amount that the solid medium after the removal of water should have the 10 minute-average water absorption rate of at least 0.05 ml/minute, and the amount of the solvent water is larger than a prescribed amount by an amount almost equal to the amount of the water to be removed. The solid medium does not cause growth inhibition of microorganisms due to drying, shows a superior water absorption rate to enable application of a larger amount of a sample in a short period of time, and is suitable for quick and accurate measurement tests of microbial numbers.