A structure of an LNG tank of an LNG carrier is provided to increase workability and productivity without using heavy reinforcement material for solving a sloshing problem. A structure of an LNG tank(40) of an LNG carrier includes upper and lower chamfers(41,42) and reinforcement boxes(45). The upper and lower chamfers are sloped at about an angle of 45 degrees for reducing lateral sloshing load of an LNG tank. The upper chamfer is formed with a height of 30% of total height of the LNG tank. The lower chamfer is formed with a height of 10% of the total height of the LNG tank. The reinforcement boxes are arranged contacting to the upper chamfer for increasing durability for the sloshing load.
