In the previous paper, we have reported the pH-dependent viscoelasticity of alkali-treated gelatin gel mixed with agar. The mixture formed a transparent and weak gel at pH below the isoelectric point (pI) of gelatin, while it formed an opaque and elastic gel at pH above the pI. Large effects of ionic strength on the viscoelasticity and the turbidity of the mixture were observed at the pH not greater than gelatin’s pI, which suggests that the mixture formed the gel via electrostatic interaction between positively charged gelatin and negatively charged agaropectin. In the present study, we examined the viscoelastic properties of acid-treated gelatin gel mixed with agar or agarose. Furthermore, direct measurements of the intermolecular interaction between gelatin and those polysaccharides were carried out by using a quartz crystal microbalance (QCM). G’ for the gelatin gel mixed with agar was strongly affected by pH. Below pH 8.5 corresponding to gelatin’s pI, the mixture of gelatin and agar formed an elastic gel with large G’. On the other hand, the mixture of gelatin and agarose formed a gel with smaller G’, and the values of G’ show weak pH dependence as compared with the mixture of gelatin and agar. It was confirmed by the results of QCM measurements that the gelatin interacts with agar at pHs below gelatin’s pI.