The present study proposes a new mechanism to cause a strong electron heating in the magnetic islands ejected from the reconnection current layer. A large‐scale full kinetic simulation in three‐dimensional system demonstrates that the electrons are effectively accelerated by the non‐ideal electric field generated through the electromagnetic turbulence excited in the magnetic islands. It is found that the high‐energy electrons are efficiently scattered by the turbulence, resulting in the strong electron heating. The existence of turbulence and the associated non‐ideal electric field in the magnetic islands is consistent with recent satellite observations in the Earth’s magnetosphere. Plain Language Summary Observed velocity distribution of space plasmas often contains high‐energy components overlapping the ambient thermal component, implying the existence of local explosive processes producing energetic particles. Magnetic reconnection is one of such the processes, converting the magnetic field energy into plasma kinetic energies. In this study, we propose a new mechanism to cause a strong electron heating in the magnetic islands generated during magnetic reconnection. By means of a large‐scale computer simulation, where both electrons and ions are treated as particles, we found that the electrons are effectively accelerated by turbulence‐induced electric field. The high‐energy electrons are efficiently scattered by the turbulence, resulting in the strong electron heating. The existence of turbulence and the associated induction electric field is consistent with recent satellite observations in the Earth’s magnetosphere. Key Points We propose a new mechanism to accelerate electrons in the magnetic islands via turbulence‐induced electric field The accelerated electrons are efficiently scattered by the electromagnetic turbulence, resulting in strong electron heating The existence of non‐ideal electric field and turbulence in the magnetic islands is consistent with satellite observations