A portable electrical device includes a tablet PC, a bottom plate, a support arm and a pivot portion. The tablet PC includes a breach and a first magnetic inducing member arranged inside the breach. One end of the support arm is pivoted to the bottom plate, and the other end of the support arm is pivoted to the pivot portion, and the other end of the pivot portion is with a second magnetic inducing member. When the second magnetic inducing member is moved into the breach to magnetize the first magnetic inducing member, the tablet PC is securely coupled with the pivot portion so that the tablet PC can be rotated; on the contrary, when the second magnetic inducing member is removed from the breach, the tablet PC can be totally independent to the support arm and the bottom plate.