A filter device for filtering dust from air includes a housing, a dust collecting module, a spraying module, and an exhaust. The housing defines an air inlet near a bottom of the housing and an air outlet near a top of the housing. The dust collecting module is installed in the housing between the air inlet and the air outlet. The spraying module is placed in the housing between the dust collecting module and the air outlet. The exhaust is connected to the housing for generating air pressure difference between near the air outlet and near the air inlet, thereby drawing and introducing air containing dust from the bottom of the housing toward the top of the housing via the air inlet.