Square vacuum dryer

The invention relates to a dryer and particularly relates to a square vacuum dryer comprising an inner box and a square shell, wherein the inner box is spherical. According to the square vacuum dryer, a square inner box is changed to a spherical structure to enable water drops condensed on the top of the inner box to flow towards two sides of the inner box along the radian of the top to the bottom of the inner box, so that the condensed water does not drop on materials to be dried, thereby effectively avoiding the return dropping problem of the condensed water and guaranteeing a relatively ideal drying effect.