Flow path forming device, extrusion device, and foamed plastic sheet

A flow path forming device, comprising:

• a first flow path forming member having a first flow path forming surface;
• and
• a second flow path forming member having a second flow path forming surface,
• wherein the first flow path forming surface of the first flow path forming member and the second flow path forming surface of the second flow path forming member form a flow path through which a plastic composition flows, and
• when a water droplet is deposited on a droplet deposition surface of each of the first flow path forming surface and the second flow path forming surface, where the droplet deposition surface is in a range from an outlet port of the flow path to 3 mm upstream in a flow direction of the plastic composition, and the droplet deposition surface on which the water droplet is deposited is tilted from a state parallel to a horizontal direction to a state parallel to a vertical direction, to measure a maximum droplet weight at which the water droplet does not slide down from the droplet deposition surface, an average value of the maximum droplet weight on the first flow path forming surface and the maximum droplet weight on the second flow path forming surface is 8 μg or more and 25 μg or less.