The present invention addresses the problem of providing malignant stem cells that can be grown in vitro and are useful in cancer therapy research and drug discovery research for cancer therapy, a method for producing same, cancer cells induced from the cells, and use for the cells. Provided are induced malignant stem cells that can be grown in vitro, the induced malignant stem cells being characterized in (1) having at least one type of abnormality selected from among (a) abnormal methylation (hypermethylation or hypomethylation) of a cancer suppressor gene or cancer-related gene region in the endogenous genome DNA, (b) somatic mutation of a cancer suppressor gene in the endogenous genome DNA or somatic mutation of an endogenous cancer-related gene, (c) abnormal expression (increased expression or decreased / lost expression); of an endogenous cancer gene or endogenous cancer suppressor gene, (d) abnormal expression (increased expression or decreased / lost expression) of non-coding RNA such as endogenous cancer-related micro RNA, (e) abnormal expression (increased expression or decreased / lost expression) of an endogenous cancer-related protein, (f) endogenous cancer-related metabolism abnormality (hypermetabolism or hypometabolism), or (g) abnormal endogenous cancer-related carbohydrate; and (2) expressing the POU5F1 gene, NANOG gene, SOX2 gene, and ZFP42 gene.