A sealant applying device and a working method thereof, and a sealant applying apparatus are disclosed. The sealant applying device includes a nozzle; the nozzle includes an air inlet portion and a sealant outflow portion, a switch plate is arranged below the sealant outflow portion, the switch plate includes a plate body configured to horizontally move between a first state and a second state, one end of the plate body is provided with a through hole, and a discharge portion is provided at a position corresponding to the through hole and on a side of the plate body facing away from the sealant outflow portion.