There may be provided a process for producing a polyimide siloxane solution composition having a further improved long-term viscosity stability; and a polyimide siloxane solution composition. In the process for producing the polyimide siloxane solution composition by polymerizing/imidizing a tetracarboxylic acid component and a diamine component consisting of (a) a diaminopolysiloxane, (b) a diamine having a polar group and (c) a diamine other than (a) and (b) in a solvent, the tetracarboxylic acid component and the diamine component excluding (b) the diamine having a polar group are polymerized/imidized to provide a reaction mixture solution, and then (b) the diamine having a polar group is added to the reaction mixture solution last, and the mixture is polymerized/imidized.