I see small hairless patches on scalp, they are many in number like dots. Is it normal or some problem. If it's problem, then please provide cure.

Sounds like. Alopecia areata, cause unknown. Ask someone to see if there are any hairs growing in the bald patch that look like an exclamation mark (broad top, narrow bottom) that are diagnostic.
? alopecia areata. It sounds like you are describing a condition called alopecia areata. It is an autoimmune process, where your body attacks your hair follicles causing them to fall out, often in discrete patches. Often the hair grows back, and generally no other problems occur. I would go see a dermatologist about the condition for a definitive diagnosis and treatment options.