This study compared the microtensile bond strength $({mu}TBS)$ of single step adhesives to different dentin depths. Superficial or deep dentin was exposed in 30 molar teeth by sectioning immediately under the DEJ or 1.5mm area from central pit, respectively. After polishing with 600-grit SiC paper, the dentin surfaces were assigned to three groups: AQ group-AQ Bond, L-Pop group-Adper Prompt L-Pop, Xeno group-Xeno III. The bonded specimens were sectioned into sticks and subjected to ${mu}TBS$ testing with a crosshead speed of 1mm/minute. The results of this study were as follows; The ${mu}TBS$ to superficial dentin was higher than that to deep dentin in all group. The ${mu}TBS$ of Xeno group was significantly higher than that of L-Pop group and AQ group in both superficial and deep dentin (p<0.05).