There is provided a pressure applying device capable of applying pressure to a working object with a substantially constant force through a compact structure. The pressure applying device includes a pressure accumulating portion; a piston including a small-diameter portion inserted into a cylinder portion on a pressure accumulating portion side, and a large-diameter portion disposed close to a working object W; and a tubular body extending from the large-diameter portion to the cylinder portion. A lubricating fluid is held inside the tubular body.

An IFP is disclosed. The IFP includes a sealing channel formed axially about an outer diameter (OD), the sealing channel including at least two walls where the at least two walls of the sealing channel having a smaller OD than an inner diameter (ID) of a chamber and a channel is formed between the at least two walls. The IFP also includes an anti-tipping feature fixedly coupled with at least a portion of one wall of the sealing channel, the anti-tipping feature increasing a length of the IFP.