To provide a water-soluble varnish composition for a polystyrene film, having excellent adhesion, physical properties of printed matter and moldability and a laminated sheet for molding polystyrene trays having a varnish coating layer formed by the varnish.

The water-soluble varnish composition for a polystyrene film includes a styrene/acrylic core-shell type emulsion (a) that has a core part and a shell part and an acid value of 30-60 and a styrene/acrylic core-shell type emulsion (b) that has a core part and a shell part and an acid value of 70-150. The laminated sheet for polystyrene trays have an unstretched polystyrene film layer, a printing ink layer, a varnish layer and a polystyrene-based sheet layer in this order in which the varnish layer is composed of the film of the water-soluble varnish.