Abstract: A block toy is composed of a plurality of blocks magnetically connectable to each other. At least one of the blocks comprises a block main body having plural flat surface portions, magnet holding portions formed on inner sides of the respective flat surface portions, and permanent magnets accommodated within the respective magnet holding portions for rotation about imaginary axes extending at right angles relative to the flat surface portions corresponding to the magnet holding portions. The magnet holding portions may be in the form of magnet holders arranged on the inner sides of the respective flat surface portions. The magnet holders may preferably be connected together so that the resulting connected magnet holder has a cross-sectional shape substantially similar to the corresponding cross-sectional shape of the block main body formed by the corresponding plural flat surface portions.