A liquefied gas tank includes an inner tank (2) that stores liquefied gas and is disposed so as to be capable of self-standing on a floor surface (F), and an outer tank (3) that is covered over the inner tank (2) and is supported by an upper face portion (2a) of the inner tank (2). The outer tank (3) is configured to be capable of sliding on the upper face portion (2a) of the inner tank (2) in response to expansion and contraction in the horizontal direction of the inner tank (2), and to be capable of moving in response to expansion and contraction in the vertical direction of the inner tank (2). A ceiling portion (3a) of the outer tank (3) that is placed on the upper face portion (2a) of the inner tank (2) is not fixed to the upper face portion (2a) of the inner tank (2), and the inner tank (2) and the outer tank (3) are configured to be capable of sliding in the horizontal direction relative to each other. The outer tank (3) includes an expansion and contraction mechanism portion (33) that is disposed along the lower outer circumference thereof.