Tunnel dust collecting device

The utility model discloses a tunnel dust collecting device which comprises a dust collecting bag and a small fan, and the dust collecting bag comprises a collecting transverse pipe and a collecting vertical pipe which are communicated in an orthogonal relation. A dust collecting inlet and a dust collecting outlet are formed in the two ends of the collecting transverse pipe respectively, and the small fan is installed at the dust collecting outlet; the interior of the collecting vertical pipe is divided into a sinking air duct and an ascending air duct through a vertical air partition plate, the lower ends of the sinking air duct and the ascending air duct are communicated, and the upper end of the vertical air partition plate extends upwards into the collecting transverse pipe to partition the collecting transverse pipe. The upper end of the sinking air duct is communicated with the dust collecting inlet, the upper end of the ascending air duct is communicated with the dust collecting outlet, and a dust filt