A bead string of tin oxide crystallite or a bead string of complex oxide crystallite of tin oxide and titanium oxide contains tantalum and has specific hue as well as a crystallite size on the order of nanometer, and exhibits excellent conductivity and improves the catalytic activity. A bead string includes a tin oxide crystal particle aggregate or a crystal particle aggregate of a complex oxide of tin oxide and titanium oxide, in which the crystal particle aggregate contains at least one particle having a crystallite size of 5 to 50 nm, and when the crystal particle aggregate is pressed under a pressure of 0.1 MPa to have a thickness of 1 cm, in the color of the resultant particle aggregate represented by Lab color space, a lightness L* value is 80 or less, a chromaticity a* value is −4 or less, and a chromaticity b* is −3 or less.