The process of building construction using concrete material is almost impossible to finished process casting at one time. Delay in mixer trucks and weather that not support is very possible in the construction of buildings, therefore cold joints cannot be avoided. The purpose of this study is to analyze flexural strength with the effect of a cold joint in beams using an experimental method. In this experiment is used three types of concrete beams such as normal concrete beams without reinforcement (control specimens), vertical failure plan and horizontal failure plan which is a concrete mix design method using ACI 211.1-19. Setting time for cold joint samples in this experiment used two different times (120 minutes and 240 minutes) and flexural strength was analyzed in 7 days, 14 days and 28 days after curing. The result from three types of specimens showed that flexural strength increases with the increasing age of concrete. Results of comparison between normal concrete and cold joint concrete that effect of cold joints can reduce the grade of flexural strength beams. Flexural strength of vertical failure plan with setting time of 120 minutes and 240 minutes decreased respectively by 8,77% and 12,25% where the average flexural strength was 7,07 MPa and 6,8 MPa compared to normal concrete amounting to 7,75 MPa. For the flexural strength of horizontal failure plan with a casting delay of 120 minutes and 240 minutes, it decreased by 4.90% and 10,45% where the average flexural strength was 7,37 MPa and 6,94 MPa.