The invention relates to the technical field of building construction equipment, and discloses an automatic sand sieving machine for building. The automatic sand sieving machine for the building comprises a machine case, a feeding hopper, a quantitative feeding device and a sand sieving device, wherein the sand sieving device comprises a motor, a cam, a sliding plate, a fixed rod and a sieving disk, the sliding plate is connected with a sliding rod, the sliding rod is connected with a first sliding block, a rotation shaft is rotatably connected onto the first sliding block, the rotation shaftis coaxially connected with a gear, the first sliding block is connected with a rack in sliding mode, the rack and the gear are meshed with each other, a second sliding block is connected onto the fixed rod in sliding mode, the second sliding block is fixedly connected with one end of the rack, the rotation shaft is connected with a rotation disk, a vertical rod is hinged with the center of the rotation disk through a spherical hinge, two connection rods are hinged at the lower end of the vertical rod, and the lower ends of the two connection rods are fixedly connected with the sieving disk. The automatic sand sieving machine for the building separates yellow sand from stone through sieving by continuously moving the sieving disk up and down and continuously swinging the sieving disk, andovercomes the problems that single vibration of an existing sand sieving mode causes low sand sieving efficiency and poor sand sieving effect in the prior art.