Tee yields, physical properties and gel formation abilities or hot-water extractable material (HWEM) and water-soluble alginate (WSA) extracted from Laminaria japonica were estimated and compared with those of the alginate (ASA) extracted with alkali solution in the routine procedure. The contents of HWEM, WSA and ASA in Laminaria japonica were 8.3, 2.5 and $19.1\%$, respectively. The HWEM and WSA had no gel formation ability, whereas the ASA had a good gol formation ability. The HWEM and WSA were almost not viscous even in $1.5\%$ of the sample solution, whereas the ASA was very highly viscous in above $0.5\%$ of sample solution. The melting points of $1\%$ solution of HWEM, WSA and ASA sample were 31, 24 and $14^{circ}C$, respectively. The solubility at melting point of each samples varied from 2.3 to 2.6 g/100 g water, and a few differences were observed.