The present invention relates to stem cells obtained by culturing monocytes in the presence of (i) M-CSF and (ii) at least one member selected from the group consisting of ganglioside and water-soluble plant-derived extract, thereby dedifferentiating the monocytes； a therapeutic agent for treating damaged cells, tissues or organs； a cell drug agent； a method of producing stem cells, a culture medium for dedifferentiating monocytes； a dedifferentiation inducing agent； a cell drug kit； a kit for producing dedifferentiated cells； and a pharmaceutical composition.
