The invention discloses a water-saving planting device and an irrigation method for plants and vegetables. The planting device comprises a water trough, a planting trough, a lifting device, a suspension wire, a wire cable, brackets and an automatic control device, wherein the water trough is a container which has a certain depth and can accumulate water; the planting trough is a device which has a plurality of small water-permeable holes and contains soil; a side pole of the planting trough can slide vertically in a rectangular hole in the side surface of the water trough; and the brackets are fixed above both sides of the water trough. The irrigation method comprises the following steps of: planting plants and vegetables in the planting hole which contains soil and has a plurality of small water-permeable holes, and filling irrigation water in the water trough below; and during irrigation, lowering the planting trough into the water trough for some time to enable water to permeate the planting trough, and after some time, using a manual or electric or hydraulic lifting device to lift the planting trough from water. The invention maintains the water saving effect of hole irrigation for seeding, and completely changes the planting device and the irrigation method thereof. The planting device can automatically carry out irrigation regularly and quantificationally, and the irrigation water can be recycled, thereby effectively lowering the irrigation cost.