To produce a bulky nonwoven fabric, comprising parts, comprising fibers, having a prescribed fiber diameter and regularly bent in the thickness direction of the nonwoven fabric and present in the width direction, etc., of the nonwoven fabric at a constant interval, having many voids, excellent in heat insulating properties and filter performances and useful as a heat insulating material, etc.

This bulky nonwoven comprises parts, comprising fibers, having an average fiber diameter within the range of 1-25μm and irregularly bent in the width direction of the nonwoven fabric and present at a constant interval of, e.g. 0.5-6.0mm in the width and/or the longitudinal directions of the nonwoven fabric. The bulky nonwoven fabric is obtained by collecting attenuated fibers on a forwardly moving perforated unit having an opening diameter of 25-5000 times that of the average fiber diameter of the fibers in a melt blowing method and taking off the nonwoven fabric while keeping the temperature of the fibers on the perforated unit in a state above the glass transition temperature of the fibers and ≤(5/6) the melting point thereof.