We investigate four electrons confined in a coupled three-layer quantum dot, by the exact diagonalization method.A vertical magnetic field to the confinement plane is considered. The ground-state electronic structures and angular momentum transitions are investigated. We find that for four-electron QDs, the series of the magic numbers in three-layer QDs are different from those in one-, and two-layer QDs. These are connected to the exchange and rotational symmetries of the systems.