The present invention aims to provide a mononuclear cell preparation material capable of improving the mononuclear cell recovery while reducing granulocyte contamination, and a mononuclear cell preparation method which improves the mononuclear cell recovery. Provided is a mononuclear cell preparation material for removing granulocytes from blood to prepare mononuclear cells, which includes a nonwoven fabric made of a polyamide resin. Also provided is a method for preparing mononuclear cells using a device with the mononuclear cell preparation material packed in a container, the method including the steps of: (A) passing blood through the mononuclear cell preparation device from an inlet side to an outlet side of the device, thereby capturing granulocytes in the device and (B) passing a washing solution through the mononuclear cell preparation device from the inlet side to the outlet side of the device, thereby recovering mononuclear cells remaining in the device.
