To provide a lid device containing a cap having the function of discharging a content of a vessel by the push-in operation of a pressing part, and properly opening the vessel by using the function.

A thin-walled breakable portion 131 is formed on an inner plug 1. The cap 2 includes the pressing part 203d capable of being pushed inward of the cap 2 by elastic deformation and a discharge part 203b discharging the content of the vessel B by pushing in the pressing part 203d. Between the cap 2 and the inner plug 1 there is a link member 203g moving inward of the vessel B by the push-in operation of the pressing part 203d. The breakable portion 131 is broken by the link member 203g moved during the first push-in operation of the pressing part 203d to make a space in the vessel B communicate with a space in the cap 2.