A mouse device includes a lateral pressure sensing unit and a base unit having a base seat, a housing, and an inner space cooperatively defined by the base seat and the housing. The base seat is elongated in a front-rear direction, and includes a bottom face portion and an extension face portion surrounding and extending upwardly from the bottom face portion, and having spaced apart first and second lateral sections. The housing surrounds the base seat, extends upwardly from the extension face portion, and includes an operating portion extending upwardly from the first lateral section and having front, rear, upper, and lower pressing regions. The lateral pressure sensing unit is located in the inner space, is adjacent to the front, rear, upper and lower pressing regions, and is triggered upon operation on the operating portion.