Dear Oki

The Tm for displayed peaks is around 82oC, which indicates presence of product. It's certainly not primer dimer. Also the Ct values are well in range, showing moderate amplification. Kindly find out Tm of your expected product.

First try to rule out chances of any contamination, involving pipettes, tips, environment. 

Secondly, you may try increasing your annealing temp. Hope it works 

That "peak" is so small and weak that it's most likely an artifact.  Did you include a positive control?  Run out your samples on a gel to see if you have an actual product (I doubt it) and include a positive control.  The software is designed to look for ANY difference in fluorescence so I'm quite certain that you are seeing an artifact and not a real product.

Dear Harsh.

Thank you for your answer. I tried to two steps-PCR( denatureation-anealing/extension) and tree step PCR. But both have similar peaks. 

I changed the water, place, sybr green reagent and primers. the patterns were same. 

Did I miss anything to solve this problem?

Dear Harsh.

Thank you for your answer. I tried to two steps-PCR( denatureation-anealing/extension) and tree step PCR. But both have similar peaks. 

I changed the water, place, sybr green reagent and primers. the patterns were same. 

Did I miss anything to solve this problem?

Dear Harsh.

Thank you for your answer. I tried to two steps-PCR( denatureation-anealing/extension) and tree step PCR. But both have similar peaks. 

I changed the water, place, sybr green reagent and primers. the patterns were same. 

Did I miss anything to solve this problem?

Dear Harsh.

Thank you for your answer. I tried to two steps-PCR( denaturation-annealing/extension) and tree step PCR. But both have similar peaks. 

I changed the water, place, sybr green reagent and primers. the patterns were same. 

Did I miss anything to solve this problem?

Dear Katie.

Thank you for your answer. 

I checked it by gel electrophoresis. the bands were smearing.

I also checked with a template( I didn't mark in here) when I did the upper experiment.

I gained same peaks as NTC's peaks.

Could you let me know what I miss it in this result?

Dear Oki

Can you let me know the product size and reaction time/temp conditions. Also can you share your gel pic. As suggested earlier, can you find out the tentative TM of your product. 

Harsh