In-Vitro Fertilization (IVF) is a procedure to obtain embryo by inseminating oocyte and sperm outside human body. Several embryos are produced at the end of this procedure and it remains a problem to select the most appropriate embryo to be implanted into uterus. Many strategies have been proposed for selection of the embryo. The latest is time-lapse microscopy which monitors the embryo development continuously. An automatic method using computer to detect and locate the position of the embryo is thus needed. In this paper, an approach based on a modification of Hough Transform using Particle Swarm Optimization (PSO) is proposed to approximate the embryo as a circle. Each PSO particle represents a circle in the parameter space and mainly used to reduce the computational complexity of Hough Transform. Experiment result showed that the proposed method is able to detect the position of the embryo accurately. The result from this method can be used to extract criteria for embryo transfer purpose.