The invention discloses flat roof rainwater collection and utilization equipment, and belongs to the technical field of environmental protection and comprehensive utilization of resources. The equipment is installed at a flat roof and is of a box body structure having the bottom closed and the top open, the top of the equipment is flush with the top of a building parapet wall, the interior of the box body is divided into an upper layer and a lower layer by a division plate, an initial rainwater tank is on the lower layer, a rainwater collection tank is on the upper layer, the upper layer is communicated with the lower layer via an initial rainwater collection port in the middle of the division plate, initial rainwater enters and fully fills the initial rainwater tank via the rainwater collection port, and clean rainwater is automatically stored into the rainwater collection tank; an initial rainwater drainage port connected with a building roof drainage port is formed in the bottom of the initial rainwater tank, and a water taking port communicated with a toilet flushing water supply pipe inside the building is formed in the bottom of the rainwater collection tank; and a switch is respectively arranged at the drainage port of the initial rainwater tank and the water taking port of the rainwater collection tank. The equipment effectively utilizes the gravitational potential energy of collected rainwater, and realizes split flow of initial rainwater and recycling of late clean rainwater.