An opening/closing body locking device for an opening/closing body that is openably/closably mounted to an opening portion of a stationary body, the locking device including locking portions provided on both lateral sides of the opening/closing body, a pair of link rods that are mounted to the stationary body, and are interlocked with each other to slidably move so that hook portions at distal ends thereof engage and disengage the locking portions, a biasing unit that biases the link rods in directions that the hook portions of the link rods engage the locking portions, and an operating member that causes the hook portions of the link rods to slide in directions that the hook portions disengage the locking portions against biasing force of the biasing unit, pressing members that are provided on the both lateral sides of the opening portion of the stationary body.