Alumina is generally used as an inorganic filler, while spinel, which is known to be lower in thermal conductivity than alumina, is used in applications such as gems, fluorescence emitters, catalyst carriers, adsorbents, photocatalysts and heat-resistant insulating materials, but not expected to be used as a thermally conductive inorganic filler. Thus, an object of the invention is to provide spinel particles having excellent thermal conductive properties. The invention relates to a spinel particle including magnesium, aluminum and oxygen atoms and molybdenum and having a [111] plane crystallite diameter of 220 nm or more.