NOVELTY - A positive electrode active material contains a boron compound and spinel-type lithium transition metal oxide. The interatomic distance of lithium and oxygen of spinel-type lithium transition metal oxide which is measured by Rietveld method is 1.971-2.006 Angstrom . The content of magnetically attracted substance of the positive electrode active material is 600 ppb or less, and is calculated by a specific method.    USE - Positive electrode active material is used for lithium battery for electric vehicle and hybrid electric vehicle (claimed).    ADVANTAGE - The lithium battery comprising positive electrode active material has excellent packaging density, power output characteristics and reduced voltage reduction during charging and storing at high temperature.    DETAILED DESCRIPTION - A positive electrode active material contains a boron compound and spinel-type lithium transition metal oxide of formula: Li1+xM2-xO4-(~d), where M is transition metal containing manganese, aluminum or magnesium, x is 0.01-0.08 and ( delta ) is more than 0. The interatomic distance of lithium and oxygen of spinel-type lithium transition metal oxide which is measured by Rietveld method is 1.971-2.006 Angstrom . The content of magnetically attracted substance of the positive electrode active material is 600 ppb or less, and is calculated by the following method: Ion-exchange water (500 cc) and single cylindrical stirring rod-type magnet coated with tetrafluoroethylene are added to positive electrode active material (powder) (100 g) in 500 cc resin container, then provided on a ball mill rotating stand and rotated, to form slurry. Then the magnet is removed, immersed in ion-exchange water, and the adhering excess powder is removed using ultrasonic washing machine. Then the magnet is taken out, immersed in aqua regia, heated at 80 degrees C for 30 minutes, and a magnetically attracted substance is dissolved, the quantity of iron, nickel, chromium and zinc in aqua regia is analyzed with an inductively-coupled-plasma-atomic-emission-spectrometry apparatus and the amount of magnetically attracted substance per content of positive electrode active material is calculated by making the total content into the amount of magnetically attracted substance. The magnetic force of the magnet which is 100-150 mT is measured using TESLA METER model TM-601.