Abstract: A pest trapping device including a cap, a spewing member, a fan, a rotatable shaft, a transformer, a tray, a blue light emitting element, an electric circuit board, and a net. The spewing member has symmetrical holes to which support rods are secured for supporting the transformer controlling the rotatable shaft to rotate and further rotate the fan connected with the shaft. The tray is placed on the support rods for holding a pest-attracting chemical. The electric circuit board is positioned on a fixing frame fixed in the cap and connected with the light emitting element and the transformer that is turned on and off by a switch on the cap. When the device is powered, pests can be attracted by a smell giving out by the volatile chemical in the tray and the yellow color of the device, and during nighttime also by the blue light emitting element and sucked in by the fan and then held in the net.