To realize a combustion state monitor device for a boiler capable of highly accurately monitoring the combustion state of a solid fuel and a combustion controller for a boiler capable of properly deciding the combustion state of the solid fuel and performing an optimum combustion control.

The combustion state monitor device for a boiler for monitoring the combustion state of the solid fuel in a black liquid recovery boiler comprises an image pick-up means which has sensitivity characteristics of the sensitivity of an infrared ray area higher than those of the sensitivity of a visible ray area and picks up the solid fuel in a sherbet state in the black liquid recovery boiler and a switching means for switching a state that infrared rays are incident on the image pick-up means and a state that visible rays are incident on the image pick-up means.