Abstract: The present invention provides a method of manufacturing leather, which not only significantly suppresses the occurrence of adhesive wrinkling and boarding/alighting wrinkling when used for an automobile seat, for example, but also exhibits appropriate flexibility.

Abstract: A natural leather is treated with a tanning agent, a re-tanning agent, a dye and a greasing agent, wherein a treatment agent for inhibiting the generation of formaldehyde and acetaldehyde from the natural leather is added to the greasing step so that the natural leather is impregnated with the treatment agent. The treatment agent includes a hydrazide compound optionally together with sodium hydrogen sulfite.

Abstract: This object relates to a natural leather which is obtained by forming a coating film through the greasing step following re-tanning and dyeing and the drying step. The purpose of this object is to provide a natural leather, wherein the generation of free formaldehyde and acetaldehyde is inhibited, and a treating agent to be added in the greasing step for natural leather. A natural leather wherein formaldehyde and acetaldehyde generated by a tanning agent, a re-tanning agent, a dye and a greasing agent having been incorporated into a leather are confined in the leather with a treating agent to be added in the greasing step for natural leather which contains a hydrazide compound optionally together with sodium hydrogen sulfite to thereby inhibit or prevent the generation of formaldehyde and acetaldehyde, and an automobile interior part coated with this natural leather.