A nuclear fuel storage rack connection structure for connecting a plurality of nuclear fuel storage racks (A, A1, A2, A3, A4), the nuclear fuel storage rack connection structure comprising: the plurality of nuclear fuel storage racks (A, A1, A2, A3, A4) which are stored so as to be arrayed underwater inside a storage pit, with nuclear fuel assemblies being accommodated in the nuclear fuel storage racks (A, A1, A2, A3, A4); a plurality of engagement receiving portions which are installed on an outer circumference of each of the plurality of nuclear fuel storage racks (A, A1, A2, A3, A4) and which have engagement holes penetrating from an upper face to a lower face of the engagement receiving portions in a vertical direction; and an engagement member includes at least two engagement leg portions which engage with the engagement receiving portions, so as to connect the mutually adjacent nuclear fuel storage racks (A, A1, A2, A3, A4), characterized in that the engagement receiving portions are installed at a plurality of stages in a vertical direction on the nuclear fuel storage rack (A, A1, A2, A3, A4) so as to be overlapped at the plurality of stages in the vertical direction, the engagement leg portions extend vertically and the upper ends of which are integrally formed, each of the at least two engagement leg portions is engaged with the engagement receiving portions by the engagement leg portion being inserted into the engagement holes of the engagement receiving portions that overlap in the vertical direction, the engagement receiving portions are multiple installed on each of the mutually adjacent nuclear fuel storage racks (A, A1, A2, A3, A4), and one end of the engagement member is engaged with the engagement receiving portion of a first nuclear fuel storage rack of the plurality of nuclear fuel storage racks (A, A1, A2, A3, A4), while the other end of the engagement member is engaged with the engagement receiving portion of a second nuclear fuel storage rack of the plurality of nuclear fuel storage racks (A, A1, A2, A3, A4). the plurality of nuclear fuel storage racks (A, A1, A2, A3, A4) which are stored so as to be arrayed underwater inside a storage pit, with nuclear fuel assemblies being accommodated in the nuclear fuel storage racks (A, A1, A2, A3, A4); a plurality of engagement receiving portions which are installed on an outer circumference of each of the plurality of nuclear fuel storage racks (A, A1, A2, A3, A4) and which have engagement holes penetrating from an upper face to a lower face of the engagement receiving portions in a vertical direction; and an engagement member includes at least two engagement leg portions which engage with the engagement receiving portions, so as to connect the mutually adjacent nuclear fuel storage racks (A, A1, A2, A3, A4), characterized in that the engagement receiving portions are installed at a plurality of stages in a vertical direction on the nuclear fuel storage rack (A, A1, A2, A3, A4) so as to be overlapped at the plurality of stages in the vertical direction, the engagement leg portions extend vertically and the upper ends of which are integrally formed, each of the at least two engagement leg portions is engaged with the engagement receiving portions by the engagement leg portion being inserted into the engagement holes of the engagement receiving portions that overlap in the vertical direction, the engagement receiving portions are multiple installed on each of the mutually adjacent nuclear fuel storage racks (A, A1, A2, A3, A4), and one end of the engagement member is engaged with the engagement receiving portion of a first nuclear fuel storage rack of the plurality of nuclear fuel storage racks (A, A1, A2, A3, A4), while the other end of the engagement member is engaged with the engagement receiving portion of a second nuclear fuel storage rack of the plurality of nuclear fuel storage racks (A, A1, A2, A3, A4).