Channel forming member and method for manufacturing channel forming member

A method for manufacturing a channel forming member in which a fluid channel is formed between a first constituent part and a second constituent part, comprising:

• injection-molding the first constituent part at a first position between a pair of molds and injection-molding the second constituent part at a second position between the pair of molds;
• opening the pair of molds so that the first constituent part remains in one of the pair of molds and the second constituent part remains in the other of the pair of molds, and then moving the pair of molds relative to each other so that the first constituent part and the second constituent part face each other;
• closing the pair of molds so that the first constituent part and the second constituent part abut each other;
• and
• pouring melt resin around an abutting portion between the first constituent part and the second constituent part, wherein
• in the pouring melt resin, the melt resin forms a bonding portion and a thickened portion,
• the bonding portion abuts the first constituent part and the second constituent part,
• the thickened portion abuts only one of the first constituent part and the second constituent part, or abuts neither the first constituent part nor the second constituent part, and
• a volume of the thickened portion is more than or equal to 50% of a volume of the bonding portion.