A production method for producing granulated materials comprises sampling step for sampling at predetermined time intervals diffracted and/or scattered light from growing particles under granulation in a granulation tank as measured particle size distribution data by applying beam light to the growing particles, calculating step for calculating the size of particle from the measured particle size distribution data by applying a specific algorithm, comparison step for comparing the particle size from the measured particle size distribution data with that from the particle size distribution objective data prepared in advance, and correction step for adding change to basic feedback control for granulation process in accordance with the result of the comparison step. And the granulated materials production apparatus comprises a granulation tank therein having a fluid bed and spray means for spraying a binder solution above the fluid bed, and sampling measurement apparatus detachable to the corresponding portion of the granulation tank, into which growing particles floating in the granulation tank are introduced for sampling.