PURPOSE: To provide the titled molding material which has excellent heat crack resistance and hardly cause discoloration by heat and warpage, consisting of a guanamine-modified melamine resin, an inorg. fibrous substrate and an inorg. non-fibrous substrate.

CONSTITUTION: 1mol of melamine, 3W4mol of formaldehyde and benzoguanamine or acetoquanamine in an amount of 1.2W1.8 times by mol that of melamine are subjected to an addition condensation reaction by heating at a pH of 8W9 to obtain a guanamine-modified melamine resin (A). 35W55pts.wt. component A is blended with 5W15pts.wt. inorg. fibrous material (B) (e.g., glass fiber), 30W60pts.wt. inorg. non-fibrous material (C) (e.g., CaCO3) and optionally, a plasticizer, a parting agent, a colorant, etc. (D).