1. A control device mounted on a projection-type video-image display device including: a projection unit that projects a video image onto a screen via a lens; an image capturing unit that captures the screen; and a focus adjustment unit provided on the projection unit and operated manually, comprising: a focus evaluation value calculation unit configured to calculate, as a focus evaluation value, a characteristic value that changes in accordance with the focus state of the video image adjusted by the focus adjustment unit by acquiring a captured image captured by the image capturing unit and then by analyzing the image; a focus evaluation value storage unit configured to store the focus evaluation value calculated by the focus evaluation value calculation unit and a target value of a focus evaluation value; and a focus state determination unit configured to determine a display color of focus state information projected onto the screen as a graph with a color indicating the degree of focus, wherein the focus state determination unit includes: a unit for acquiring the focus evaluation value stored in the focus evaluation value storage unit and calculating a change of the focus evaluation value; and a unit for determining focus state information to be displayed by referring to a table that associates a combination of the change of the focus evaluation value, the focus evaluation value, and the target value with the display color of the focus state information.