The invention relates to the technical field of building materials, and discloses a device for efficient painting building indoor latex paint. The device comprises a shell, a button is fixedly connected to the exterior of the shell, a whitewashing opening is formed in the surface of the shell, an operation handle is fixedly connected to the exterior of the shell, a rotating wheel is movably connected to the interior of the shell, a sliding groove is formed in the surface of the rotating wheel, and the interior of the shell is fixedly connected to a sliding rail. Through interaction of the whitewashing opening, the operation handle, the rotating wheel, the sliding groove, the sliding rail, a sliding plate, a detection rod, a rolling wheel, a connecting plate, a U-shaped magnetic plate, an electromagnet, a rotating plate, a spraying plate, a nozzle, a rolling brush, a tank body, an electromagnetic pump, a photosensitive assembly and a detection assembly, the thickness of latex paint painted on the wall can be kept consistent, the situation that the flatness of latex paint painting is affected by technical experience of constructors, and consequently large difference is generated is effectively avoided, the quality of latex paint painting is improved, and furniture users can enjoy better decoration experience.