Research has been carried out to study a photo-conductive properties of indium antimonide (InSb) as a detector, working in the IR region at 3-6u.m. Wafer of P-type has been taken from single crystal of [220] direction. Sample preparation started with Mechanical treatment for its faces has been carried out to reduce surface defects. A chemical compound of HNO3,.HF and CH3COOH has been placed for 30 seconds to help electrode connection on the surface followed by coating the surface using coating; unit by aluminum film. A study has been performed for the parameters with darkness and brightness at room temperature. High response was noticed at 6iim wavelength. The measured of D* for the detector was 1.95* 108 cm Hz1/2/W at room temperature. The conclusion behind this study that the InSb crystal prepared under the condition defind by this investigation that crystal can work as a IR-detector in the region of 3-6um.