Yes,washing machine can be kept in balcony but in case the balcony is built with rise walls or iron handrails and should use isolating slabs for saving it of outer circumstances as heat of the sun and rain etc, as well as it is important to use tempered glass or blinds .On the other hand ,it is not prefer to keep the washing machine in balcony because the washing machine could be harmed by the sun, wind and rain,as a result to erosion, flaking of the dyes and furthermore harm to the quite sensitive electronic appliances and control boards.