Generally, wool sweaters suggest dry cleaning. If the care label indicates that it can be machine washed, you can wash it, but do not wash it too frequently.
It is recommended to hand wash the wool sweater, as machine washing can easily cause shrinkage and deformation.
Before washing, turn the wool sweater inside out to reduce friction on the fabric.
Keep the water temperature below 30°C (86°F). Avoid using hot water, as high temperatures can cause shrinkage and pilling. Use lukewarm water below 30°C and add a neutral detergent, soaking for 10 minutes. (Wash separately, do not mix with other clothes to avoid color bleeding.)
Wash gently by hand, without scrubbing or wringing. Focus on the areas like cuffs and neckline, which can be gently rubbed.
After rinsing, do not wring the sweater by twisting it or use a washing machine for spinning. Instead, use a clean towel to press out excess water. (Do not lift the sweater with one hand, as a wet wool sweater is heavy and could deform.)
Lay the sweater flat in a drying rack and air-dry in a shaded area. Avoid drying in direct sunlight. (Do not hang it on a regular hanger, as it can cause deformation.)