To provide a washing agent for a molding machine using an inorganic foaming agent inexpensive as compared with an organic foaming agent to achieve cost reduction and having a washing capacity and easy substitution properties of a degree equal to or higher than those of a case using the organic foaming agent and capable of washing an extrusion molding machine.

The washing agent for the molding machine is composed of 30 to 95 wt.% of a thermoplastic resin A and 5 to 70 wt.% of a resin composition containing the inorganic foaming agent and a thermoplastic resin B. The ratio (B/A) of the melt flow rates of the thermoplastic resin B and the thermoplastic resin A is 50 or above.

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