An object of the present invention is to provide a model mammal for diabetes onset, being useful for elucidating the onset mechanism of diabetes caused by a blockage of signal transduction from insulin, and for the development of a remedy for said diabetes, and to provide a screening method of a remedy for said diabetes. A diabetic-prone transgenic mouse is prepared in a process comprising the steps of: a transgene that contains a Meg1/Grb10 gene, an imprinted gene exhibiting maternal expression, or a human GRB10 gene in the downstream of a chicken .beta.-actin promoter and in the upstream of a rabbit .beta.-globin poly A is constructed, and subsequently the transgene is microinjected into a male proneucleus of a mouse fertilized egg; thus obtained egg cell is cultured and then transplanted into an oviduct of a pseudopregnant female mouse; after rearing up the recipient animal, baby mice that have the above-mentioned cDNA are selected from the mice born from the recipient animal.