A control rod for a boiling water reactor is provided with a structure element having mutually-perpendicular four blades. The four blades have a neutron absorber-filling region that neutron absorber is held, respectively. In the structure element, a plurality of regions formed in an axial direction of the control rod include a first region having a first cross-section that forms a first united cruciform cross-section of the four blades connected one another, a second region having a second cross-section that has each separated cross-section of the four blades, and a third region having a third cross-section that has a second united cross-section of continuous two blades of the four blades, disposed in a diametrically opposite direction and facing each other and each separated cross-section of remaining two blades of the four blades, disposed perpendicularly to the continuous two blades.