The utility model discloses an auxiliary platform device applied to tunnel construction. The device comprises a plurality of stand columns fixedly arranged on the ground in the vertical direction. A cuboid frame is defined by the multiple stand columns. Main beams are fixedly arranged above the multiple stand columns in the two long edge directions of the cuboid frame correspondingly. A pluralityof secondary beams are evenly arranged between the two main beams, a working panel is fixedly laid on the secondary beams, a crawling ladder is obliquely arranged at one end of the working panel, guardrails are arranged on the periphery of the working panel, and an anchor throwing opening, a soil discharging opening and a lifting opening are formed in the working panel. Two guide rails are arranged on the two sides of the working panel, and a conveying platform capable of doing reciprocating motion along the two guide rails is erected on the two guide rails. The working panel has a large construction space, the lower frame is stable in structure, flexible movement of construction machinery on the platform can be guaranteed, and tunnel construction can be carried out faster and more orderly.