PURPOSE: A joist structure is provided to supplement the weakness of wood and to reduce the failure rate of wood by forming a metal reinforcement pipe and square wood integrally, thereby improving strength. CONSTITUTION: A joist structure(100) comprises: a metal reinforcement pipe(110) formed in a rectangular shape of the appointed length and formed in a hollow; wood(120) formed in the square bar shape of the corresponding length to the length of the reinforcement pipe and adhered closely to one side of the reinforcement pipe; a fixing band(130) fixing the reinforcement pipe and the wood integrally by banding the reinforcement pipe and the outer circumference of the wood at regular intervals; and an impurity inflow prevention member(140) sealing up two ends of the reinforcement pipe to prevent the inflow of impurities.
