A design of a box-type solar cooker was modeled and tested in the region of Sfax-Tunisia. This solar cooker was designed to allow reaching relatively high temperatures during days with low solar radiation owing to four outer reflectors. A mathematical model, which is based on thermal balances, was developed and implemented in a Matlab program to predict the thermal performances of the solar cooker. Several tests were effectuated in order to validate the robustness of the mathematical model and to determine the thermal performance of the solar cooker. The obtained results showed an acceptable matching between the experimental temperature values and the computed temperature values with a maximum error inferior to 4%. It was also proven that the use of four outer reflectors improved the optical efficiency of the solar cooker. Indeed, the first figure of merit passed from 0.07 to 0.14 and the maximum temperature of the absorber plate passed from 81.3 degrees C to 133.6 degrees C. The sensible loading test revealed that the calculated second figures of merit for different water loads were in the range of 0.34-0.39. Finally, two real cooking process were carried out where 72 min and 107 min were required to fully cook rice and beans respectively.